Xenomorphs

"You still don't understand what you're dealing with, do you...? The perfect organism... Its structural perfection is matched only by its hostility..."

- Ash on the Xenomorph.

The Xenomorph XX121 species, more commonly known as Xenomorphs, are the main antagonists of the Alien film franchise, consisting of the films Alien, Aliens, Alien 3, Alien: Resurrection and Alien: Covenant. They also serve as the main antagonists of the non-canon crossover film Alien vs. Predator, and as minor characters in the 2012 spinoff Prometheus.

They are a hostile and parasitic extraterrestrial species that are known for their acidic blood, their pharyngeal jaw and their biological life cycle, in which their offspring are implanted inside living hosts before erupting violently from their chests, which is in many ways their most disturbing feature. Xenomorphs are asexual, with a fertile Queen producing Xenomorph eggs. The Xenomorphs are predators with the goal of expanding their own species and killing or infecting any life they encounter.

History
Unlike many of the alien invaders that came before them, the Xenomorphs did not seek conquest or human slaves, instead Xenomorphs were depicted as animal-like killers of the highest order - extremely intelligent and cunning but guided by a desire to hunt, kill and breed rather than anything more complex. Unfortunately for any species that gets in their way the Xenomorphs cannot reproduce without a very gruesome method of parasitic infection in which alien "face-huggers" attach themselves to a victim and inject them with a Xenomorph seed that grows inside their stomach, eventually bursting out of the victim as a "chest-burster" - this is, of course, fatal to the host - the "chest-burster" then proceeds to grow into a full-grown Xenomorph a short while after being "born".

Xenomorphs have several adaptations that make them even more terrifying - thick exoskeletons and amazing speed are only the start as their blood is highly acidic and they can use their tails as effective whips or stabbing implements plus they have an extendable tongue with a set of teeth on it that can be fired out with enough force to pierce a human's skull.

Xenomorphs also absorb a small amount of DNA from their host bodies before being born and this can result in unique breeds of Xenomorph being formed - such as the "dog xenomorph" or the powerful Predator/Alien hybrid the Predalien that served as the main villain of Aliens vs. Predator: Requiem.

Another creature (presumed a Xenomorph) known as the Deacon was also a cross of Engineer and Trilobite DNA born in the Alien prequel Prometheus.

A final note on Xenomorphs is that they are usually portrayed as having a matriarchal system ruled by a single Queen, the Xenomorph Queen is gigantic and powerful - seen as the most powerful of all Xenomorphs, though there may be more than one Queen as several have appeared in the movies and associated media - all varying slightly in size and appearance. In comics, there are also Queen Mothers, type of Xenomorph Queen that regarded as some sort of goddess of Xenomorphs due to her telepathic powers enable her to controlled every single existing xenomorphs around the whole universe, or at least that was she capable to do.

The Alien design is credited to late Swiss surrealist and artist H. R. Giger, originating in a lithograph called Necronom IV and refined for the series' first film, Alien. The species' design and life cycle have been extensively added to throughout each film.

Origin Story Theories
Xenomorphs' origins is mystery. There are no solid facts as to the origins of these creatures; instead, there are many assumptions which cannot be confirmed. Based on the limited information we have so far, the most commonly accepted hypothesis is that they are an artificially created species, although another hypothesis says that they evolved naturally on a planet much different than our own. Another theory is the Deacon from Prometheus evolved into the first primitive Xenomorph, though there is evidence stating that this is false in the sequel, but this at least gave the hint where Xenomorphs are actually product of bio-engineering.

Bio-Engineered Theory
In Prometheus, Xenomorphs may created via Chemical A0-3959X.91 – 15 that found in Engineers' spaceship, which also the starship model that contained Xenomorph eggs discovered by Ripley and his friends years later. This implied that Xenomorphs may a bioweapon produced via the said chemical. To be specific, the android, David, infected Charlie Holloway with a drop of the mutagen and Charlie then impregnated Elizabeth Shaw, process that creating a Trilobite, creature that may a first pre-Xenomorph lifeform. Elizabeth in pain from the lifeform growing within in her, then removes the Trilobite by entering the automated surgery table on board Meredith Vicker's exclusive ship. The Trilobite later encounters an Engineer and seeds him much like a facehugger; thus, creating Deacon, creature that may serve as prototype/beta version of Xenomorph following the known cycle of life.

Following proofs that implies creatures in Prometheus film and Xenomorph being bio-engineered products of A0-3959X.91 – 15 are:
 * All are associated with Engineers, creator of A0-3959X.91 – 15 chemical.
 * Hammerpede's acidic blood are similar with Xenomorphs'
 * Trilobites' ability to impregnating other creatures to create Deacons are reminiscent with Facehuggers' for creating Chestbursters.
 * Deacon's own characteristics that looked like alternate version of Xenomorphs'.

Should this theory proved true, Xenomorph could be the result of genetic manipulation by Engineers as a terraforming mechanism/doomsday weapon about 10 million years ago, but apparently it went horribly wrong. As a result, over the years, the Xenomorph has become an entirely new species in the galaxy. This theory has been twisted slightly by Prometheus, when the Mala'kak brought containers filled with an unknown substance (it closely resembles Xenomorph secretions in hives). This substance mutated harmless organisms into somewhat hostile creatures. When humans "infected" with this substance mate with one another it produced a different subspecies of "octo-facehuggers" that can grow incredibly large.

In newly released film Alien: Covenant, the first three prequel Alien film series, Xenomorphs are confirmed to be product of A0-3959X.91 – 15, confirming the fact that they actually bio-engineered creatures. However, up to this point, it is debatable whether David 8 the synthetic was responsible for creation of first Xenomorphs or rather (albeit unknowingly) recreating Engineers' past experiments that created either their own version of Xenomorphs or at least similar hostile endoparasitoid creatures as the movie merely revealed A0-3959X.91 – 15 as vital component to creating Xenomorphs. However, the said film's novelization revealed that David 8 referenced his experiment with those of Engineers' past Xenomorph bio-engineering experiments, which strongly contradicts the final film and Ridley Scott's comments that implied him to be sole creator and therefore, taking no references from Engineers' previous experiments with A0-3959X.91 – 15 to create hostile endoparasitoid lifeforms.

What we know so far about these endoparasitoid creatures as told in Alien: Covenant, after landing on the Engineer homeworld with Shaw, he unleashed some A0-3959X.91 – 15 vials secured from Prometheus mission against Engineers, killing them and affect the local flora that led to the formation of certain fungus-like growths that upon being disturbed released spores that infected any and all animal life, leading to the gestation of Neomorphs, feral cousins of Xenomorph race. The planet also hosted a certain endoparasitic wasp-like arthropod which was also affected by the mutagen. Over the following decade, David continued to conduct experiments on the endoparasitic wasps and Neomorph specimens using the Chemical A0-3959X.91 – 15, eventually resulting in the creation of Protomorph Facehuggers, but was stalled in his research, needing a living host to serve as an incubator for his creation. Following the birth of a Protomorph, prototype strain of his Xenomorph race creations, David infiltrated the USCSS Covenant colony ship intending to continue his experiments using the crew and colonists.

Apex Predator Theory
Another theory, commonly accepted but only in expanded universe, is they were the alpha predator of their own ecosystem on a nightmarish and harsh planet (some assume it to be Xenomorph Prime, but there is no solid evidence). Without their native ecosystem to keep them in check, they have since infested their own kind, and developed into a separate dominate species.

Concept and creation
The script for the 1979 film Alien was initially drafted by the late Dan O'Bannon and Ronald Shusett. Dan O'Bannon drafted an opening in which the crew of a mining ship are sent to investigate a mysterious message on an alien planet. He eventually settled on the threat being an alien creature; however, he could not conceive of an interesting way for it to get onto the ship. Inspired after waking from a dream, Shusett said, "I have an idea: the monster screws one of them," planting its seed in his body, and then bursting out of his chest. Both realized the idea had never been done before, and it subsequently became the core of the film. "This is a movie about alien interspecies rape," O'Bannon said on the documentary Alien Evolution, "That's scary because it hits all of our buttons." O'Bannon felt that the symbolism of "homosexual oral rape" was an effective means of discomforting male viewers.

The title of the film was decided late in the script's development. O'Bannon had quickly dropped the film's original title, Star Beast, but could not think of a name to replace it. "I was running through titles, and they all stank", O'Bannon said in an interview, "when suddenly, that word alien just came out of the typewriter at me. Alien. It's a noun and it's an adjective.". The word alien subsequently became the title of the film and, by extension, the name of the creature itself.

Prior to writing the script to Alien, O'Bannon had been working in Paris, France for the late Chilean cult director Alejandro Jodorowsky's planned adaptation of Frank Herbert's 1965 classic science-fiction novel Dune. Also hired for the project was the late Swiss surrealist artist H. R. Giger. Giger showed O'Bannon his nightmarish and monochromatic artwork, which left O'Bannon deeply disturbed. "I had never seen anything that was quite as horrible and at the same time as beautiful as his work," he remembered later. The Dune film collapsed, but O'Bannon would remember Giger when Alien was greenlit, and suggested to the director Ridley Scott that he be brought on to design the Alien, saying that if he was to design a monster, it would be truly original.

Giger's Alien, as portrayed by the late Bolaji Badejo in Ridley Scott's 1979 film Alien by 20th Century Fox. After O'Bannon handed him a copy of Giger's 1977 book Necronomicon, Scott immediately saw the potential for Giger's designs, and chose Necronom IV, a print that Giger completed in 1976, as the basis for the Alien's design, citing its beauty and strong sexual overtones. That the creature could just as easily have been male or female was also a strong factor in the decision to use it. "It could just as easily fuck you before it killed you", the said line producer Ivor Powell, "[which] made it all the more disconcerting.". 20th Century Fox was initially wary of allowing Giger onto the project, saying that his works would be too disturbing for audiences, but eventually relented. Giger initially offered to completely design the Alien from scratch, but Scott mandated that he base his work on Necronom IV, saying that to start over from the beginning would be too time-consuming. Giger signed on to design the adult, egg and chest-burster forms, but ultimately also designed the alien planetoid LV-426 and the Space Jockey alien vessel.

Giger conceived the Alien as being vaguely human but a human in full armor, protected from all outside forces. He mandated that the creature have no visible eyes, because he felt that it made them much more frightening if anyone could not tell they were looking at you. Giger also gave the Alien's mouth a second inner set of pharyngeal jaws located at the tip of a long, tongue-like proboscis which could extend rapidly for use as a dangerous weapon. His design for the creature was heavily influenced by an aesthetic that he had created and termed bio-mechanical, a fusion of the organic and the mechanic. His mock-up of the Alien was created using parts from an old Rolls Royce car, rib bones and the vertebrae from a snake, molded with plasticine. The Alien's animatronic head, which contained 900 moving parts, was designed and constructed by the late special effects designer Carlo Rambaldi. Giger and Rambaldi would both go on to win the 1980 Academy Award for Visual Effects for their design of the Alien.

Scott decided on the man-in-suit approach for creating the creature onscreen. Initially circus performers were tried, then multiple actors together in the same costume, but neither proved to be scary. Deciding that the creature would be scarier the closer it appeared to a human, Scott decided that a single, very tall, very thin man be used. Scott was inspired by a photograph of the late Leni Riefenstahl standing next to a 6'4" (1.93 m) Nubian. The casting director found 7'2" (2.18 m), the late rail-thin graphic designer Bolaji Badejo in a local pub. Badejo went to tai chi and mime classes to learn how to slow down his movements.

Giger's design for the Alien evoked many contradictory sexual images. As the critic Ximena Gallardo notes, the creature's combination of sexually evocative physical and behavioral characteristics creates, "a nightmare vision of sex and death. It subdues and opens the male body to make it pregnant, and then explodes it in birth. In its adult form, the alien strikes its victims with a rigid phallic tongue that breaks through skin and bone. More than a phallus, however, the retractable tongue has its own set of snapping, metallic teeth that connects it to the castrating vagina dentata.".

Name
This creature has no specific name, and has been referred to most often onscreen, and in the credits of each film, simply as the Alien. It was called an alien, and an organism, in the first film. It has also been referred to as a creature, a serpent, a beast, a dragon, a monster, or simply a thing. The term xenomorph (lit. "alien form" — from Greek xeno- or "strange" and -morph, shape) was used by the character Lieutenant Gorman in Aliens and by Ellen Ripley in a deleted scene from Alien 3. This term has been adopted by fans and used in merchandising as a convenient name. The species' binomial names are given in Latin as either Internecivus raptus (meant as "murderous thief") in the Alien Quadrilogy DVD or Lingua foeda acheronsis (meant as "foul tongue from Acheron") in some comic books. The main Alien from Alien vs. Predator is listed in the credits as "Grid", after a grid-like wound received during the film from a Predator's razor net.

Characteristics
Continuing advancements made in the field of special effects technology as the series progressed have led to numerous variations in the creature's design, including varying numbers of fingers and limb joints and varying head design. Characteristic that explained in this section mainly focus on Drones or Warriors.

Appearance
When standing upright, Xenomorphs are vaguely bipedal in form, though they adopt a more hunched, quadrupedal stance when walking or sprinting. They have a skeletal, biomechanical appearance and are usually colored in muted shades of black, blue or bronze. Xenomorphs do not radiate heat, as their body heat matches the ambient temperature of the environment in which they are found. In most of the films, adult Xenomorphs have the ability of running and crawling along ceilings and walls. They have great physical strength, having been shown to be capable of breaking through vent covers and welded steel doors, and even of breaking down reinforced pressurized doors.

The Xenomorphs' primary weapon is their inner pharyngeal jaw, which is capable of shooting from their mouth like a piston with sufficient power to smash through bone and metal. In fact, a common tactic used by the creatures to eliminate prey is to restrain the victim with their hands, immobilizing them, before killing them with a precision jaw strike to the head, piercing through the skull and penetrating the brain; this form of attack is colloquially known as a "Headbite". On several occasions, Xenomorphs have been seen to suspend those that they kill from the ceiling through unknown means

Xenomorphs have segmented, blade-tipped tails. The sharp tip was initially a small, scorpion-like barb, but from Aliens onwards the blade design increased in size and changed in appearance to more closely resemble a slashing weapon. From Alien Resurrection onwards, the tails have a flat ridge of spines at the base of the blade. This was introduced to help them swim convincingly, and was left intact in the subsequent crossovers. The original shooting script for Aliens and the novelization both featured a scene in which Lieutenant Gorman is "stung" by the barb tail and rendered unconscious; in the final cut of the movie, Gorman is instead knocked out by falling crates. As a weapon, the strength of the tail is very effective, having been shown to be strong enough to impale and lift a Predator with seemingly little effort. They are also adept at using their tails as blunt weapons, sometimes to deadly effect, as seen in Alien.

They have elongated, cylindrical skulls, but possess no visible facial features other than their mouth, though in the original Alien film, the top of the creature's head was translucent, with a human skull forming the front, including empty eye sockets visible within (although this is hard to distinguish on-screen). This element was reused for the "Predalien" in Aliens vs. Predator: Requiem 29 years later. How the creatures see or otherwise rationalize their environment is uncertain. In Alien 3, a fisheye lens was used to illustrate the Xenomorph's point of view. In the novelization of the movie Alien, the creature is held mesmerized by a spinning green light for several minutes. In Aliens, the adult creatures have a more textured head rather than a smooth carapace. In the commentary for Aliens, James Cameron states that this change is a part of the maturation of the creatures, as the creatures in the film had been alive far longer than the original Alien. The smooth design of the carapace would be used again in Alien 3 and Alien Resurrection. This design would be kept in Alien vs. Predator, and abandoned in Aliens vs. Predator: Requiem in favor of the ribbed design.

Throughout their appearances, human-spawned Aliens have been shown to have a fluctuating number of fingers. In Alien, the creature has webbed, six fingered hands. In Aliens, the number of fingers is reduced to three (two "paired" and a single, opposable thumb), and they are shown to be much longer and more skeletal. In Alien: Resurrection, the number of digits is increased to four, with two long middle fingers and a pair of thumbs. This design is kept in the Alien vs. Predator films, though the hands were made bulkier in order to make the Aliens seem more formidable against the Predators.

The spines on the Xenomorph's back provide protection from attacks from the rear.

Aliens have been alternately portrayed as both plantigrade and digitigrade organisms, usually in accordance to their host. Human-spawned Aliens were usually portrayed as having humanoid hind limbs, while in Alien 3, the featured Alien sported double-jointed legs due to its quadrupedal host. This characteristic would be continued in Alien Resurrection for the human-spawned Aliens. Tom Woodruff, who had previously played the "dog-alien" in Alien 3, described the human-spawned Aliens in Resurrection as feeling more like a dog than the previous creature, despite having been born from human hosts. The human-spawned Alien warriors would revert to a plantigrade posture in Alien vs. Predator.

Blood and secretions
Xenomorph blood is an extremely potent molecular acid that can corrode on contact almost any substance with alarming speed. It is dull yellowish-green in color, and seems to be pressurized inside the body, so that it spurts out when punctured. Shusett suggested the idea that the creature have acid blood as a plausible means to make the creature "unkillable"; given the starship setting, if one were to use traditional firearms or explosives to attack it, its blood would eat through the hull of the ship. In later films in the series, the Xenomorphs are shown to be conscious of the effects of their acidic blood, and even use it to their advantage — in Alien Resurrection, two Xenomorphs escape a cage by killing a third so its acid melts through the cage floor; in Alien vs. Predator a queen being held by chains apparently instructs several Xenomorphs to slash and cut her, thus corroding the chains. Had this tactic not her idea, it would have been Grid's, a Drone whom discovered corrosive nature of his kind's blood.

Xenomorphs Drones can produce a thick, strong resin (vomited from their mouths) referred as Hive Webbing that they use to build the Hives and to cocoon their victims. Its non-uniform, bio-organic appearance allows adult Xenomorphs to camouflage themselves when at rest, to the extent that humans have stood directly beside hiding Warriors and had no idea of the imminent threat. In the case of Hives set up inside existing non-Xenomorph structures, webbing helps to disguise existing visual cues in the environment, turning the area into a disorientating maze and making escape from and/or assaults on the Hive all the more difficult. However, whether this is considered by the Xenomorphs during construction is unclear. The structure of a Hive also appears to have a disrupting effect on motion tracker operation, generating a host of false readings that imply the entire area is awash with sporadic movement, making genuine readings harder to spot. The exact cause of this is unclear. In Alien vs. Predator: Extinction, it's explained that each portion of Hive Webbings within a certain radius has a living core called Hive Nodes, comprising of small organisms secreted by the Drones, which secreted by the Drone. The node's presence also enable any injured Xenomorphs to regenerate into a full health as long as they remain within its webbings' contact. Once deposited, the node uses up available organic materials from plants, carcasses, and even microorganisms to produce the hive's structure, cementing their hostility to all non-xenomorph lifeforms and has potential to corrode away an entire planet. While able to regenerate from damage, the nodes are suspectible to fire, and thus can only be effectively destroyed via complete incineration. Should a Hive Node is destroyed, the webbings it produced would wither away and rendered useless.

In the original Alien, the Facehugger is shown to be able to "spit" acid, melting the faceplate of Kane's helmet and allowing the creature immediate access to the inside. This ability is also exhibited by adult Xenomorphs in Alien 3 and Alien Resurrection; much like a spitting cobra, the creatures use this ability to blind and incapacitate their victims rather than kill them outright. This also serves as long range weapon as means to fight against foes/potential hosts that armed with guns and prefer to fight from distance.

Despite their own immunity to their blood, they are vulnerable to hydrofluric acid which was used against them to great effect on LV178.

Intelligence and communication
During events in Aliens on the LV-426 colony and in Alien Resurrection on the USM Auriga, the species displayed observational learning and problem solving skills, and in both cases the Aliens learn how to operate machinery at a very basic level. On LV-426, they were able to cut power in a section of the complex to gain access to the humans, and the Alien Queen learns to board an elevator by observing Ripley and Newt escaping in the one beside it. The novelization of the film notes that the queen establishing her 'nest' at the base's main power plant could have been chosen either for the feral, animal reason of the warmth that it would provide or for the intellectual reason of selecting a location where any attackers would be unable to destroy her without destroying the entire facility. In the director's commentary for Aliens, James Cameron noted that the creatures in Aliens had been alive for far longer than the Alien in the original, and had more time to learn about their environment. On the USM Auriga, the Aliens kill one of their own, using its blood to melt through their enclosure and escape; in Alien vs. Predator, they use a similar strategy to free the queen from her chains. An Alien also uses acid spurting from its severed tail as an improvised weapon, indicating they are fully aware of the effects of their acid blood.

Life cycle
Aliens are eusocial life-forms with a caste system ruled over by a queen. Their life cycle comprises several distinct stages: they begin their lives as an egg, which hatches a parasitoid larval form known as a facehugger, which then attaches itself to a living host by, as its name suggests, latching onto its face. In the Alien 3 novelization, Ripley commented that this parasitoid would likely be able to use a host as small as a cat, or as large as an elephant (like Oswocs in Alien vs. Predator: Extinction).

The facehugger then "impregnates" the host with an embryo known as a "chestburster", which, after a period of gestation, erupts violently from the host's chest resulting in the death of the host.

The chestburster then matures to an adult phase, shedding its skin(entering cocoon state in Alien vs. Predator: Extinction) and replacing its cells with polarized silicon. Due to Horizontal gene transfer during the gestation period, the Alien also takes on some of the basic physical attributes of the host from which it was born, allowing the individual alien to adapt to the host's environment.

The adult phase of the Alien is known by various different names. The adult Aliens have been referred to as "drones," "warriors," "workers," and sometimes "soldiers," similar to the way ants have been defined. The names of the adult phase have also been used to name different types of adult phases of the Alien in numerous sources including video games, comic books, novels, and, of course, the films, but only in the commentaries by the team who created the films. No official name has been given to the adult stage of the Alien in the films themselves.

Queen
Queen Aliens are significantly larger and stronger than the normal adults, approximately 4.5 meters (15 ft) tall. Their body structure differs also, having two pairs of arms, one large and one small. The queen's head is larger than other adult Aliens and is protected by a large, flat crest, like a crown, and they vary from queen to queen. In the second film Aliens, unlike other adults and queens, the queen had high-heel protrusions from its feet.

Egg-laying Alien queens possess an immense ovipositor attached to their lower torso, similar to a queen termite's. Unlike insect queens, there appears to be no need for drones to fertilize an Alien queen's eggs. When attached to its ovipositor, the queen is supported by a "biomechanical throne" that consists of a lattice of struts resembling massive insect legs.

In the original cut of Alien, the Alien possessed a complete lifecycle, with the still-living bodies of its victims converted into eggs. However, the scene showing the crew converted into eggs was cut for reasons of pacing, leaving the ultimate origin of the eggs obscure. This allowed Aliens director James Cameron to introduce a concept he had initially conceived for a spec script called Mother, a massive mother Alien which laid the eggs and formed the basis for the Aliens' life cycle. Cameron conceived the Queen as a monstrous analogue to Ripley's own maternal role in the film. In that vein, some critics have compared it to Grendel's mother.

The design of the queen was created by Cameron in collaboration with special effects artist Stan Winston, based upon an initial painting Cameron had done at the start of the project. The Winston Studio created a test foam core queen before constructing the full hydraulic puppet which was used for most of the scenes involving the large Alien. Two people were inside working the twin sets of arms and puppeteers off-screen worked its jaws and head. Although at the end of the film the queen was presented full-body fighting the power-loader, the audience never sees the legs of the queen, save those of the small-scale puppet that appears only briefly. In Aliens, Cameron used very selective camera-angles on the queen, using the 'less is more' style of photography. Subsequently the movie won an Oscar for Visual Effects. An adult queen was to reappear in Alien Resurrection. The original mechanical head previously used in Aliens was provided by Bob Burns, and was an altered design. It was repainted with a blend of green and brown, giving it a shimmering, insect-like quality (due to the said queen are actual clone from the original version like her children). This color concept would be abandoned in Alien vs. Predator in favor of the original black color scheme.

In the climax of the 2004 film Alien vs. Predator the queen's basic design was altered to make it more "streamlined" in appearance and its overall size was increased to 6 meters (20 feet) tall. Additional reason for this was due to Queen in the movie are far older than the one in Aliens. Other changes include the removal of the "high-heel" protrusions on its legs, including additional spines on its head and making its waist thinner because there was no need for puppeteers inside its chest. The animatronic laying queen had 47 points of hydraulic motion.

Aliens vs. Predator: Requiem (2007) introduced a younger form of the full grown queen, albeit with traits inherited from its Predator host. Recalling the facehugger's method of embryo implantation, the Predalien uses its inner mouth to directly deposit multiple chestburster embryos into pregnant female hosts, also using its mandibles to latch on the faces of said hosts. This is explained by the Brothers Strause as a means of quickly building an army of Aliens before the young queen evolves into its sedentary, egg-laying state.

Egg
The eggs laid by the queen are ellipsoidal leathery objects between 2 feet (60.96 cm) to 3 feet (91.44 cm) high with a four-lobed opening at the top. As a potential host approaches, the egg's lobes unfold like flower petals, and the parasitic facehugger extracts itself from the egg and attaches itself to the potential host. Giger initially designed the eggs with a much more obviously vaginal appearance, complete with an "inner and outer vulva". The producers complained that Catholic countries would ban the film if the allusion was too strong, so Giger doubled the lobes to four, so that, in his words, "seen from above, they would form the cross that people in Catholic countries are so fond of looking at". The interior of the original egg was composed of "Nottingham lace", which is the lining of a cow's stomach. In the first film, the quick shot of the facehugger erupting from the egg was done with sheep's intestine. Initially, the egg remained totally stationary save for the hydraulic movement of the lobes; however, by Alien Resurrection the entire egg was made to ripple as it opened.

Eggmorphing
There is another method in creating egg without any need of Queen's presence which called eggmorphing. Though this method of reproduction was ignored by official sources after its early shots of the scene that shows how this method works were cut (though partially reinstated in Director's Cut version of Alien), the novelization of the Alien 3 states that both forms of reproduction are typical of the species, and that either can be used to create more Xenomorphs, dependent on the situation. For instance, had a drone arrived in foreign lands/planet where it was only one of its kind that present with that lands/planet, it would immediately use this method for creating a Queen.

The process was unclear, but it is obvious that victim that would turned into an egg not need to morphed alive, but rather killed first. Quotes from Ridley Scott seem to imply that Eggmorphing actually involves the human "host" serving simply as a source of nutrients or "yolk" for the growing Egg (which feed on the host like a parasite), rather than physically becoming the Egg itself, as is typically assumed.

Facehugger
A facehugger is the second stage in the Alien's life cycle. It has eight long finger-like legs which allow it to crawl rapidly, and a long tail adapted for making great leaps. These particular appendages give it an appearance somewhat comparable to chelicerate arthropods such as arachnids and horseshoe crabs.

The facehugger is a parasitoid; its only purpose is to make contact with the host's mouth for the implantation process, by gripping its legs around the victim's head and wrapping its tail around the host's neck. Upon making contact, the facehugger tightens its tail around the host's neck in order to render it unconscious through oxygen deprivation. The facehugger then inserts a proboscis down the host's throat, supplying it with oxygen while simultaneously implanting an embryo. Attempts to remove facehuggers generally prove fatal, as the parasitoid will respond by tightening its tail around the host's neck, and its acidic blood prevents it from being safely cut away. In addition, its grip on the host's head is strong enough to tear the host's face off if it is forcibly removed.

Once the Alien embryo is safely implanted, the facehugger detaches and dies.

Giger's original design for the facehugger was a much larger creature with eyes and a spring-loaded tail. Later, in response to comments from the filmmakers, Giger reduced the creature's size substantially. At first Giger assumed that the facehugger would wrap around the outside of the astronaut's helmet, but Scott decided that it would have far more impact if the facehugger were revealed once the helmet was removed. Scott and Giger realized that the facehugger should burn through the helmet's faceplate with its acid blood; subsequent redesigns of the space helmet included a far larger faceplate to allow for this. Dan O'Bannon initially conceived the facehugger as somewhat resembling an octopus, possessing tentacles. However, when he received H. R. Giger's designs, which substituted tentacles with fingerlike digits, he found Giger's design concept to be superior. Since no one was available at the time, O'Bannon decided to design the facehugger prop himself. The technical elements of the musculature and bone were added by Ron Cobb. Giger's initial design for the smaller facehugger had the fingers facing forward, but O'Bannon's redesign shifted the legs to the side. When the foam rubber sculpture of the facehugger was produced, O'Bannon asked that it should remain unpainted, believing the rubber (which resembled human skin) was more plausible.

In Aliens, the facehuggers were redesigned by the late Stan Winston so that they would be capable of movement. Unlike the creatures in the first film, the creatures would take a much more active role in impregnating their victims. When Ripley throws one off her, the facehugger was now capable of scuttling across the floor and leaping at its prey, wrapping its tail around the victim's throat. Due to the film's budget, only two fully working facehuggers were built.

In Alien 3, another addition, a "super-facehugger" that would carry the embryo of the queen Alien, was planned but ultimately dropped. The super-facehugger is briefly glimpsed in the Assembly cut of Alien 3, but not identified as such. This face-hugger's role in carrying the Queen embryo are equivalent with Praetorian Facehuggers, though instead carrying embryo that grown into the queen straight away, the said embryo would grown into Praetorians, the miniature version of the queen.

Chestburster
After implantation, facehuggers die and the embryo's host wakes up afterwards showing no considerable outward negative symptoms. Symptoms build acutely after detachment of the facehugger, the most common being sore throat, slight nausea, increased congestion and moderate to extreme hunger. In later stages where the incubation period is extended in preparation of a queen birth, symptoms will include a shortness of breath, exhaustion, and hemorrhaging (detectable through biological scanners and present in nosebleeds or other seemingly random bleeding incidents), as well as chest pains inflicted either in lack of chest space due to the chestburster's presence, or even premature attempts to escape the host. The incubating embryo takes on some of the host's DNA or traits, such as bipedalism, quadrupedalism or possessing the mandibles of a Predator and other body structure changes. Over the course of 1 to 24 hours, indeterminable in some cases, and sometimes up to a week, in the case of some queens, the embryo develops into a chestburster, at which point it emerges, violently and fatally ripping open the chest of the host. There is no on-screen explanation of the reasons for the different incubation times.

The chestburster was designed by Alien director Ridley Scott and constructed by special effects artist Roger Dicken. Giger had produced a model of a chestburster that resembled a "degenerate plucked turkey" and was far too large to fit inside a ribcage. Much to Giger's dismay, his model reduced the production team to fits of laughter on sight. Scott drafted a series of alternative designs for the chestburster based on the philosophy of working "back from the adult to the child" and ultimately produced "something phallic." The chestburster in the original Alien was armless but arms were added in Aliens to facilitate the creature crawling its way out of its host's corpse. This concept would be abandoned in Alien Resurrection and subsequent films.

Growth and maturity
When a chestburster erupts from the body of its host, it is less than 1 foot (30 cm) tall. However, it soon undergoes a dramatic growth spurt, reaching adult size in a matter of hours; in Alien the chestburster had grown to 2 meters (6.6 ft) in height by the time the Nostromo crew located it again. The chestburster is shown to have molted before reaching maturity. In Aliens vs. Predator: Requiem Alien warriors are shown who are still growing, showing shedding skin. In the unrated cut, the Predalien is shown actively wiping off its final molted skin at the film's start.

Alternative forms
Aliens take on various forms depending on the characteristics of their hosts. Most of the Aliens seen to date have been human-spawned, but a number of Aliens born from other hosts and newly created variants have also been seen. This also includes those that exclusively seen in video games and comic book series of both the main franchise or AVP franchise.

Dog Alien
The quadrupedal Alien variant from Alien 3. The "Dog Alien" (also jokingly referred to as the "Bambi burster", or "Runner Alien" in the expanded universe stories), was introduced in Alien 3. The creature itself shares the same basic physical conformation and instincts as the other Aliens shown in the previous films, although there are several differences due to the host it was spawned from (a dog in the theatrical cut, an ox in the DVD assembly cut). The Dog Alien in its Chestburster form is a miniature version of the adult, unlike the larva-like human spawned chestbursters. The adult is primarily quadrupedal, has digitigrade hind legs and lacks the dorsal tubes of the human-spawned variety.

Concept and credit controversy
Originally, H. R. Giger was approached on July 28, 1990 by David Fincher and Tim Zinnemann, and was asked to redesign his own creations for Alien 3. Giger's new designs included an aquatic face-hugger and a four-legged version of the adult Alien. Giger said in an interview; "I had special ideas to make it more interesting. I designed a new creature, which was much more elegant and beastly, compared to my original. It was a four-legged Alien, more like a lethal feline – a panther or something. It had a kind of skin that was built up from other creatures – much like a symbiosis." However, when Tom Woodruff and Alec Gillis of Amalgamated Dynamics told Giger that they had their own design, Giger expressed himself as "very upset" and that the creature he had especially designed was his "baby". Even after the production severed contact, Giger continued to fax suggestions to Fincher, and made full-scale drawings and a sculpt of the Alien, all of which were rejected.

"David Fincher neglected to inform me that Woodruff and Gillis were also contracted to take care of the redesign of the Alien – I found out much later... I thought I had the job and that Woodruff and Gillis would work from my plans. On their side, they were convinced that it was their job and accepted my 'suggestions' with pleasure. They believed that all my effort was based on a huge love for the matter, because I worked hard even after my contract was over."

Giger would later be angered by the end credits of the released film presenting him as merely the creator of the original creature, and the fact that ADI personnel gave a series of interviews that minimized Giger's contribution. Fox eventually reimbursed Giger, but only after he refused to be interviewed for their behind-the-scenes documentary of Alien 3.

The Academy Awards overlooked Giger's contribution to Alien 3. However, Ridley Scott included Giger's name along with nominees Carlo Rambaldi and Richard Johnson. Fox, at the time Alien 3 was released, pointed out that studios are precluded from submitting nominees in the effects category directly to the Academy. This upset Giger so much that at one point he sent Academy president Karl Malden a fax with this closing comment: "I am under the strong impression that my contribution to the visual effects of the nominated movie has been intentionally suppressed", signing the letter with a large black pentagram.

Giger however would comment that he thought the resulting film was "okay" and that the Alien was "better than in the second film."

Newborn
In Alien Resurrection, due to significant genetic tampering in an attempt to recover DNA from the deceased Ellen Ripley and the Alien Queen within her, the resulting cloned Aliens show a number of minor human traits. The cloned Queen inherits a womb, and as a result it ceases to lay eggs and gives birth to a humanoid mutant. Physically, the human-Alien Newborn is very different from its brethren, being larger, with pale, translucent skin, a skull-shaped face with eyes, a human tongue and complete absence of a tail. The Newborn fails to bond with its Alien Queen mother, and kills it. Instead, the Newborn sees the Ripley clone as a surrogate parent.

The Newborn creature was originally scripted by Joss Whedon as being an eyeless, ivory-white quadruped with red veins running along the sides of its head. It had an inner jaw, with the addition of a pair of pincers on the sides of its head. These pincers would have been used to immobilize its prey as it drained it of blood through the inner jaw. The creature was also meant to rival the Queen in size. Jean-Pierre Jeunet later asked ADI to lean towards making the human-Alien hybrid, known as the Newborn, more human than Alien. The Newborn's eyes and nose were added to improve its expressions to make it a character, rather than just a "killing machine", and give it depth as a character. Jeunet was adamant about the Newborn having genitalia, a mix of both sexes. However, Fox was uncomfortable and even Jeunet felt "even for a Frenchman, it's too much." The genitalia were digitally removed in post-production. The Newborn animatronic required nine puppeteers and was the most complex animatronic in the film.

Predalien
This variation is the result of a facehugger impregnating a Predator. The "Predalien" was first depicted in a painting by Dave Dorman, and subsequently featured in the Aliens vs. Predator comics and games. A Predalien chestburster debuts in the final scene of Alien vs. Predator, but it is not seen until Aliens vs. Predator: Requiem that an adult hybrid makes its first movie appearance.

The Predalien shares many characteristics with its host, such as long hair-like appendages, mandibles, skin color and similar vocalizations. It is a large, bulky creature, and possesses physical strength greater than that of human-spawned Aliens. Like human-born Aliens, it is also shown to be stronger than its host species, as evidenced by its ability to pin, push, and knock a Predator away with ease.

The Predalien seen in Aliens vs. Predator: Requiem was also a Queen, as it also possessed the ability to impregnate human hosts with multiple Alien embryos before molt into a true Queen.

Other Versions of Predaliens
Other versions of predaliens however, instead depicted as a young Queen like the one in Gunnison, are instead portrayed as heavy shock troopers. This was due to them, unlike Gunnison Predalien, lacks ability to impregnate other species nor a Queen. Instead, they use their strengths for dealing the heavy blow upon their enemies.

Notable alternate versions of Predaliens that portrayed like this are the Abomination and Predalien in AVP: Extinction.

Deacon
Ridley Scott's 2012 film Prometheus, originally conceived as a direct prequel to Alien, ends with the birth of a creature noted for its similarity to those in the Alien franchise. Scott christened the creature the "Deacon" in reference to its oblong head, which resembles a bishop's miter. Designer Neal Scanlan said that the Deacon's appearance had to reflect its complex genetic heritage: "It came from Shaw and Holloway, which then produced the Trilobite, which impregnated the Engineer, which then mixed its DNA with the Trilobite. We tried to hold on to some of Shaw, some femininity since it was born of a female before being born of a male.". According to Scanlan, the Deacon "represented the beginning of Giger's Alien, although it did not directly resemble that creature". The designers based the Deacon's skin on horse placenta, in an effort to give it an iridescent quality "between horrific and beautiful". Its pharyngeal jaw was inspired by that of the goblin shark.

When discussing the film's connection to Alien, the cowriter named Damon Lindelof asked: "Do you need to see a xenomorph bursting out of the human body? And how do we do it in a way that you haven't seen before?" Lindelof stated that whether the creature is a queen Alien, or the progenitor of the eggs found by the crew in the original Alien, is open to interpretation, but said, "I felt that the punchline of Prometheus was going to be that there is human DNA in what we have come to know as the human xenomorph."

Neomorphs
Neomorphs are creatures which unlike Deacon, are true sibling of both Protomorphs and original Xenomorph race. They are indirectly created by David 8 when polluted Engineers' settlement on Paradise, and had important role in his experiments for Protomorph creation.

In terms of behavior, the Neomorph is far more feral and animal-like than a typical Xenomorph, to the point that even their newborn form is highly aggressive and dangerous when they will attack anyone on sight. Their animalistic nature may suggest a lack of intelligence in comparison to their counterpart. Unlike the Xenomorphs, Neomorphs are more organic in appearance and lack biomechanical aspects. Neomorphs are notably seen consuming the flesh of humans they have killed unlike Xenomorphs who more concerned in expanding their hive and amassed an army of their brethren while rarely eating their enemies' flesh.

According to David 8, the Engineer's black liquid mutagen was intended to create hybrid creatures like the Neomorph that would instinctively hunt down and kill all non-botanical, animal life in an ecosystem - "the meat". Notably, when one Neomorph encountered David 8, it apparently recognized that he was a synthetic android - and thus instead of attacking him, simply stood still and regarded him in confusion. Xenomorphs, in contrast, have been observed attacking synthetics - possibly another example of their greater intelligence compared to Neomorphs, whose behavior seems to be based more on animal instinct.

Neomorph Eggsack
Pollution by black liquid produced a numbers of Neomorph Eggsacks on the ground. These Eggsacks looked like small, black, spherical, fungus-like growths on the ground that when disturbed would release a cloud of microscopic spores (motes) into the air.

Neomorph Motes
Neomorph motes are microscopic spore-like embryo that came out from an eggsack in response of it being disturbed. Once came out, they flew and entered nearby host organism through any open orifice — such as the nostrils or ear canal.

Bloodbursters and Adulthood
Once a host is infected with the airborne contagion, the spores would enter the bloodstream and proceed to developed into a Bloodburster to grow inside of them until they violently puncture the skin and claws their way out of the host's body. This process is notably similar to the Xenomorph Chestburster, although the exact point of emergence varies depending on how the host was infected. For instance, should the spore entered the ear, it will bursts out of the host's head.

Initially, the creature is born with arms and legs and moves in a quadrupedal manner, reminiscent of a Runner, but as they grow, the Neomorph adopts a bipedal stance. The creature has pale whitish-gray skin with a somewhat translucent appearance, attributes that resemble those of a Hammerpede. The Neomorph features a fleshy tail tipped with spikes, which can be used as a devastating slashing and battering weapon, and a large number of silvery fangs in their mouth, which appears circular when closed. Notably, individual Neomorphs appear to display physical variance. For instance, one of the creatures featured a pair of sharp, bony dorsal spikes on their back that assisted them in breaking out of their host, whereas the other individual encountered lacked these features. Their blood is thick and yellow in color, but notably not acidic.

Unlike a typical Xenomorph, Neomorphs do not possess an extendable inner jaw which can be used to attack. Also, while the teeth of a Xenomorph's outer jaws are usually visible, a Neomorph's jawline is nearly invisible when closed.

Protomorphs
David's Xenomorphs (also known as Protomorphs) are strains of xenomorphs he personally created, which confirmed the fact that Xenomorphs are products of Engineers' black liquid with a parasitic wasp as genetic material to create his first xenomorphs. While virtually identical to original Xenomorph strain featured so far, this Xenomorph strain possesses notable differences that set it apart from its mainstream cousins due to more crude appearance than another. Notably, they lack any biomechanical features and their limbs are longer, thinner and muscular, with gaps appearing in their arm pits. The shoulders and dorsal tubes are noticebly different, being smaller and thinner. David's Xenomorphs also has a thinner, sleeker tail that ends with a small barb or stinger.

Even with these differences, these Xenomorph strains still as deadly as their cousins since they share same powers and abilities, including their armor-piercing inner jaws.

Protomorph Eggs
Protomorph Eggs looked similar with mainstream strains', but had more crude appearance.

Protomorph Facehuggers
Protomorph Facehuggers had more crude appearance than regular facehuggers because area where reddish wrinkled area between forelegs had flat smooth surface with the same coloration as the rest of its body instead of reddish wrinkled look. The digits are notably different as they are thinner and while their actual span may be the same as typical Facehuggers, the size in between knuckles is different, notably the size of the digits from body to the first knuckles is smaller. Protomorph Facehugger also weaker than regular facehuggers due to easily removed from the victim's face and they were slow in strangling the victim with the tail, but makes up of this weakness with their incredible speed and agility and ability to impregnate its host within seconds of attachment that made their ability to a host alive and in a coma redundant, otherwise optional as they would only need to remain attached long enough to implant the Chestburster. Though share the same recklessness with regular facehuggers, protomorph facehugger was intelligent enough to analyze its situation: One of these facehuggers shown quickly retreating when the targeted host too aggressive, but upon seeing another viable host, it immediately sprang from its cover and attacked.

All in all, protomorph facehuggers' physiology is more designed for speed and hasty infestation instead of incapacitating.

Protomorph Chestbusters
The differences in the Drone of this Xenomorph race extend to its Chestburster form (which had more developed limbs like Dragon the Runner Xenomorph in Alien 3).

Praetorians
Alternate form of mature xenomorph that so far, only appeared in video games. In appearance, Pretorians can be considered as miniature version of the Queen due to their similar color and physical structures. Unlike Queens, however, Praetorians do not possess a second pair of arms on their chest, and their jaws, filled with metallic teeth, are comparable to lower Xenomorph castes. Like Queens, Praetorians typically possess longer dorsal tubes that end in a sharp point when compared to other Xenomorphs that possess these appendages. Praetorians are dark in color, typically black but sometimes blackish-blue, and stand over 10 feet (304.80 cm) tall, towering over their fellow Xenomorphs on the battlefield. Despite this size, they are almost as fast and agile as their smaller Xenomorph siblings. Although, Praetorians seem to remain in a permanent bipedal position, and owing to their bulk, they cannot scale walls or ceilings.

As is befitting of their size, Praetorians are incredibly strong and their thick skin, known to be bulletproof in some cases, enables them to shrug off damage that would be terminal several times over to most other Xenomorph castes. They are capable of defeating entire squads of human Marines single-handed and are even a match for Yautja in close-quarters combat. Praetorians can spit acid in far larger quantities than other Xenomorphs, and will also use their claws and long blade-tipped tails as slashing and stabbing weapons, making them deadly at any range. In Aliens vs. Predator, the Praetorian's upper jaw protrudes slightly, giving them an overbite.

In AVP: Extinction, Praetorians can be upgraded so they can molt into two specialized breeds as their alternate life cycle: Carriers and Ravagers:

Carriers
Carriers are alternate life cycle of Praetorian that purposed for field infestation. Should be noted that in spite of majorities of xenomorphs could subdue their foes/preys that can be used for impregnation by facehuggers, it does not guarantee that they always succeed in doing so, as sometimes they ended up killed before able to took the said potential hosts back into their hive. Other problems would be that the facehugger themselves (though able to travel from the hive into the outside world) are vulnerable and can be easily killed. Carriers' presence within the hive would could counteract this, as they could bring around six to twelve facehuggers for instantly subdued potential hosts on the field without truly need for bring them back into the hive.

Carriers resemble Drones in appearance, but are thrice taller and lack clawed fingers. Instead, they possesses a single blade on each arm much like a praying mantis. Also, they possesses pairs of dorsal tubes that seemingly have joints on them, and generates nutrients for facehugger to feed on board. Carriers also use these tubes to propel the facehuggers on their foes' face like catapult. Had Carriers facing enemies that cannot be infested, whether while carrying facehuggers or not, they uses their blades instead.

Ravagers
Ravagers are presumed to be the Xenomorph evolutionary response to the heavier military equipment brought to bear by more advanced species. This massive beast towers above other Xenomorphs, short of the queen, and has a uniquely terrifying presence in battle. Instead of just having hands, its upper extremities terminate in "hull blades" capable of easily slicing through even advanced armors and metals. Their appearance are depicted as a taller and more muscular version of warriors.

Unlike other forms of Xenos, purpose of a Praetorian molting into one of these are solely for combat alone, as it can only killed their foes outright instead subdue them: Ravagers' attacking methods often in form of beheading any enemies that they encountered.

Mutated Chestburster
A mutated Alien variant incapable of maturing past its larval stage, the mutated chestburster resembles a large black Chestburster. Hatched from a pink egg among an ordinary clutch, the mutated chestburster's egg was smuggled to the pleasure planet Celeste, where the resulting hatchling, after escaping from a human host, caused havoc among the population with its diseased slime trail, which caused people to go delirious and detonate.

Swimmer Xenomorphs
In Aliens Colonial Mariness story published by Dark Horse Comics, a group of marines ends up on a colony planet known as 'Bracken's World', a primarily oceanic planet that grows large amounts of sea kelp. Having become stranded on one of the kelp beds following an APC breakdown, the group is attacked from the water by large xenomorphs resembling queen aliens from the top half, and a more whale-like structure below the waist with a lateral tail fin and several trailing tentacles.

White Hybrids
The hybrids are a race of Aliens created by a corrupted computer system called "Toy". The hybrids possess the traits of Aliens, Predators and humans. Like Aliens, they are a eusocial species with acid for blood (though it is less acidic than that of the ordinary strain) and like humans, they are capable of speech and can use firearms. They are led by a hybrid king which generates facehuggers capable of impregnating ordinary Aliens.

Eloise
Eloise is a vat grown prototype Alien/humanoid android hybrid created using Queen DNA on Sybaris 503, who escapes from the destruction of the facility after an attempted "hostile" take over. She later settles on the planet LK176 with her group of "implanted" lepers (whose condition prevents their chestbursters from maturing) and a pack of Alien warriors. She and her army successfully beat back both Predator and human forces (at the cost of most of her leper friends), and she gives the latter an ultimatum to leave her people alone, or be destroyed.

Queen Mother
Queen Mothers are the supreme rulers of the Xenomorph species, and even Queens are subordinate to them. They appear in Dark Horse's extended universe, albeit only on the Hiveworld, where they are protected by enlarged, elite drones. Queen Mother's nests consist of six orbs arranged around a central orb, in which they reside. These orbs are interconnected and contain the prized royal jelly, which molts a drone or warrior into a new Queen Mother when one becomes absent. Queen Mothers have acute telepathic and emphatic abilities, thus they are able to call to their hive over vast distances. In fact, the Queen Mother was capable of melding to the minds of humans during the Earth infestation. What makes a Queen Mother similar to a Queen is that they are both capable of laying eggs. The first Queen Mother was kidnapped by Ripley in Steve and Stephanie Perry's novel The Female War, leading to anarchy and chaos on the Hiveworld. While a drone was morphing to take the previous Mother's place, several deviant, drones, designated as "red drones" by the humans due to their dull, burgundy color, were born that rebelled against the primary hive, and a countering red hive, led by a red Queen Mother, was created. In Aliens: Genocide, massive warfare has broken out between the two subspecies over rule of the planet as the dominant xenomorph species. A fleet of Colonial Marines (financed by the Grant Corporation, Weyland-Yutani's competition in the Aliens novels) were sent on a mission to retrieve the deceased Mother's royal jelly, located in the "black" hive, in order to synthesize a highly addictive drug called Xeno-Zip, also known as Fire (which the government felt was a "highly useful" combat drug). The crew decided to destroy the red Mother's hive to distract the drones of the original nest while the jelly was being extracted. The new Queen Mother was shot after killing a scientist during the extraction.

Rogue Alien
In the comic Aliens: Rogue, a mad scientist engineered the Rogue Alien: a male alien designed as a weapon to rival the queen caste and thus help rid the Earth of its alien infestation (see Earth Hive, Nightmare Asylum, Female War, and Genocide). However, the engineered Alien King escapes and wreaks havoc until it is killed by the Queen that had been nesting in a separate and secured section of the installation.

In the book of the same name, the Rogue is believed to be more powerful than the Queen, but Dr. Ernst Kleist, the scientist who created the Rogue, is shocked to find the Queen is in fact the superior specimen. While the Rogue is larger and stronger, the Queen's superior speed and intellect enable her to easily dodge the Rogue's brutish attacks while she slowly wears it down and finally slaughters it. Kleist is subsequently killed when he uses a sound cannon (a sound device he designed to [and that did] instantly freeze the movements of xenomorphs) on the Queen until it goes critical, destroying the asteroid-base he is on. The Rogue is seemingly much more aggressive and mercilessly attacks the smaller castes of Aliens. This is illustrated when Professor Kleist finds the crushed corpses of the elite Praetorian guard of the queen. The Rogue's recklessness is shown when it destroys the barrier that separates the Alien sector and the Human sector, thus allowing any Alien drones that escaped the Rogue's notice to pour into the Human sector, and when it confronts the queen by crushing the eggs in its way while the queen carefully steps around them to outmaneuver the Rogue.

Empress
The Empress is a later stage in the xenomorph life cycle not specifically stated. When a hive expands to the point of having multiple queens that dwell in it, the "Empress" is the queen that the subsequent queens had spawned from, making the Empress the "queen of queens." The Empress is somewhat larger than most other queens and boasts a larger crest than the rest. The crest of an Empress has an addition pair of straight spines that flank the three spires of its crest, and there appears to be not as many curves to the crest as there are with the crests of other queens; there are much more geometric lines and angles.

Matriarch
The queen dubbed the "Matriarch" is the oldest known alien queen. It is unknown how old the Matriarch is specifically, but many speculate that she could be thousands or perhaps hundreds of thousands of years old. The Matriarch's flesh has yellowed and wrinkled with age, giving the creature a subtle softness to its exterior. The crest of the Matriarch has also expanded with age: two pairs of spires fan out to the sides of the crest in addition to the three that all queens seem to have at maturity, and a bony ridge of spines runs down the center of the crest sweeping towards the end of it. The face of the Matriarch is extensively scarred as well and missing chunks of flesh from around the mouth and the carapace that protects the face when it is retracted has holes in it that resemble being eaten away by acid.

Arachnoid
A strong purple and black brood that uses powerful jump attacks. They are assumed to be special variants of the Warrior and Stalker aliens created through experimentation, much like the Chrysalis and Razor Claws minibosses. They are sometimes seen curled up on the ground as they wait for enemies.

Chrysalis
A very large (around the same size as a Praetorian) Xenomorph with a grayish-green exoskeleton and a hard, tan carapace on its head, back, and forearms. It sometimes moves/attacks by rolling itself along the ground in a ball. It gets its name from the chrysalis that it is seen gestating in when it first appears. The Chrysalis' head can actually extend a short distance from underneath the carapace over its head when biting its prey, in addition to the extension of the inner mouth. More Chrysalis are also seen defending the Queen during the final battle. These have a reddish or blue coloring.

A variation of the Chrysalis appears in the second level of the Konami "Aliens" arcade game, but it looks considerably different and has a different attack pattern.

Defender
A bluish brood with an apparently hardened carapace on its arms and head that can defend itself against most projectiles and hand-to-hand attacks.

Dogburster
A lighter colored variation of the Runner from Alien 3; a "Super" Dogburster also appears as a much tougher version that launches purple balls of acid from its mouth.

Flying Xenomorphs
Castes of Xenomorphs that born with ability to flight by the wings. They can be seen in Konami's Aliens, the arcade game Aliens: Extermination as a boss under the name Alien Dragon, in the Super Nintendo game Alien vs. Predator as an end-level boss (this one having gestated in a giant species of bat and taken on the arm-wings and overall appearance of a bat), as well as a Flying Queen in the Kenner toy line.

Infectoids
A human implanted by a type of facehugger altered as a bioweapon. Instead of being sedated, they are put in a zombie-like state, and move around the nesting area, attacking any intruders (presumably either hypnotized by facehugger that implanted them through chemical secretions or possessed by chestburster inside them). If the same type of facehugger implants a Predator, the Predator is instead driven into a berserk state, and will attack anything that moves. Similar zombie-like humans controlled by aliens are found in the Female War comic book, the Aliens arcade game and Alien trilogy for Playstation.

K-Series Xenomorphs
In Aliens Verses Predator: Extinction, a variation of the original xenomorphs are created by Dr. Samuel Kadinsky. This group is called "The K-Series". They are almost identical to normal xenomorphs in ability but have white and yellow pigmentations to their exoskeleton rather than the dark colors usually seen. They were eventually wiped out in a hive war to keep the species of xenomorphs "pure" (being that they were not naturally created, but were instead clones).

Tarkatan Xenomorphs
This unique Xenomorph breed is from Mortal Kombat X and it started it's life as one of the eggs that left behind by members of it's kind on Outworld long ago, until a Tarkatan Patrol leader disturb one of them. This egg hatch in response, releasing the facehugger inside that immediately latches on his face. Later, after the facehugger had fallen off, the Alien progeny burst from the unfortunate Tarkatan's chest, bearing characteristics of both Xenomorph and host.

It eluded the rest of the Tarkatan soldiers and eventually killed them with both of it's inherent powers and and the newfound one, retractable blades that it gained from its Tarkatan host. The creature now roams Outworld, looking for more hosts to build the hive and amasses more powerful Xenomorph breeds to take over Outworld.

Individual
Xenomorph individuals are Xenomorphs given names or something similar making them their own being compared to their caste


 * Nostromo Drone
 * First Acheron Queen
 * Second Acheron Queen
 * The Cloned Queen
 * Sevastopol Drone
 * Xenomorph Drone (Alien: Isolation)
 * Antarctic Queen Xenomorph
 * The Matriarch
 * Lead Alien
 * Grid
 * The Dragon
 * Gunnison Predalien
 * The Abomination
 * Mozart
 * Trixie
 * Ryushi Queen
 * Ryushi Predalien
 * Ol' Blue
 * Satan

Weaknesses
In spite of their notorious nature do have so weaknesses and therefore, not invincible:


 * Due to their dependence with the hosts for multiplying, the hive will not able to repopulate had potential hosts in their territory are scarce or no longer available. Had this happened after the hive sustained huge damaged after invasion done by either human soldiers or predators and the surviving xenomorphs' number became scarce, they will have major disadvantages.
 * Majorities of known Xenomorph breeds are fighting in close quarters, which means firearms are effective weapons against them, though the recommended firearms must either nitrogen weaponries, napalm weaponries, or guns with equal firepower with either M4A1 Pulse Rifle or better (it is ill-advised to only used hand guns or combat knifes, even if it works for kill the weakest xenomorph forms like facehugger or chestbursters).
 * However, Napalm weaponries (like flamethrowers) are far more effective as their bodies are weak to fire.
 * Heavy weaponries with firepower that equivalent with either rocket launcher, plasma weapories, or laser guns are also effective for dispatching multiple xenomorphs at once, but is recommended to kept for used against stronger breeds/castes like queens or predaliens.
 * In either way, one must ensure to both keep their distance (3-4 meter are recommended) away from the xenomorphs as well as not positioned themselves right in front of them for these reasons:
 * Warrior xenomorphs' pressurized bloodstream will cause it to burst apart upon killed by guns, drenching nearby enemies in acid blood.
 * Acid_Spit.gif castes like drones or runners could spit acid as means to counteract their weaknesses in close-range combat.
 * Queens are primary source of eggs within the hive as without her, the hive would suffer the huge loss. Things would be worse had there are no surviving eggs/facehuggers after their hive attacked as well as no xenomorphs that capable to mold into replacement queen.
 * The last, but not least, xenomorphs' caustic blood are useless fighting against another member of their kind or in least extent, predators' weaponries that constructed from acid-resistant materials. This forced them to resort to fight with their bladed tails, claws, and inner jaws.

Cultural impact
A memorial to the Alien in Vladivostok, Russian Far East. In the years since the release of Alien, the Alien has become one of the world's most recognized movie monsters and a pop-cultural icon. In June 4, 2003, the Alien was voted as the 14th most memorable screen villain by the American Film Institute. The Blondie co-founder Chris Stein, who is a friend of Giger, pondered in an interview:

"I'd like to see someone even vaguely compile how many versions of the Alien are floating around the world in models and stuff; there must be close to 100,000–little toys, things. All the Japanese horror comics just plunder his style."

- H.R Giger

Examples of Alien-inspired works include the classic video games Contra and Metroid.


 * The Aliens have appeared in many crossovers (including a large number of intercompany crossovers) in comic books and other media such as novels, toys, and videogames. Crossovers include encounters with Terminators, Judge Dredd, Green Lanterns, Batman, and Superman. The largest of these crossovers is the Alien vs. Predator franchise, in which the Aliens battle the Predators. This was an idea that came to the comic book artist Chris Warner in early 1989. He and other people at Dark Horse Comics were trying to come up with a good character combo for a new comics series. Dark Horse had been publishing Aliens comic book under license from 20th Century Fox since 1987. In November 21, 1990, the first depiction of the idea in film appeared in Predator 2, when an Alien skull, sculpted by Kevin Hudson, appeared as one of the trophies in the Predator spacecraft. Because Dark Horse possessed the rights to the franchise in comics, it has been able to feature likenesses of the alien in its other licensed comic books. For example, it did this in a mini-issue of Buffy the Vampire Slayer Season Nine which was billed in the media as an Alien crossover.


 * Giger's Alien was iconic enough to have an audio-animatronic version of it appear in The Great Movie Ride at Disney's Hollywood Studios at Walt Disney World in Orlando, Florida. The Alien appeared with the attraction's opening in May 1, 1989 and remained there until its closing in August 13, 2017. An Alien-based attraction at the Magic Kingdom entered early development stages before being reworked into ExtraTERRORestrial Alien Encounter until its closing in October 12, 2003.


 * In the Red Dwarf episode Polymorph, the Polymorph turns into a form that looks similar to the Xenomorph in one scene.

Animaniacs
A Xenomorph appears in the episode Taming of the Screwy. It attempts to attack Dot Warner, but Dot released her pet (red monster with horns) from her box to protect her. A Xenomorph and Dot's pet monster fell in love with each other and leaves Dot.

South Park
A Xenomorph appears in South Park's Imaginationland Trilogy, The Xenomorph was among with the other evil imaginary characters who break through the barrier which destroyed by the terrorists using Rockety Rocket causing the evil imaginary characters to be free. The Xenomorph kill the Mayor of Imaginationland and later join up with the other evil imaginary characters in the war against the good imaginary characters.

Conker's Bad Fur Day
A Xenomorph appears as the final boss of the game. Heinrich is the final boss in the game. After Berri gets shot by Don Weaso, the Panther King starts to have stomach pains. He is oblivious to what is going on, but all of a sudden, his breath cuts short, starts coughing weakly and, after seconds passed, he gets a horrible surprise. A black, reptilian figure with a tail bursts out of the Panther King's chest, instantly killing him. Professor von Kriplespac starts to call the creature "Heinrich" and then orders him to kill Conker. Conker then runs over to a nearby lever and pulls it, opening up the air vault, where Berri's body, The Panther King and Von Kripplesac get sucked into space (Don Weaso's fate is unknown) and Conker runs out the room to don a heavy Spacesuit to battle Heinrich.

Conker then tries to defeat him by throwing him into space, but to no avail does he get sucked in. After throwing him out two more times, Heinrich gets his grip and is climbing back up and powerfully pounces at him like a panther, where the game then freezes up. Conker contacts a game programmer and agrees to keep the lockup a secret in exchange for help beating Heinrich. Conker is transported to the Panther King's throne room and allowed to choose any weapon he wants to defeat him. After grabbing and storing a Shotgun and a crossbow, he chooses a katana and decapitates Heinrich before the dangerous weapon can kill him, causing acidic green blood to burn up part of the floor. After that, Franky comes out of nowhere, looks at a dead Heinrich on the floor and says that Conker is now king and was never seen again.

Kill la Kill
A Xenomorph makes a cameo appearance in Episode 16 of the anime series, Kill la Kill as one of Mako Mankanshoku's "transformation" sequences.

Insaniquarium
One of the Aliens called Sylvester appears to be inspired by the Xenomorph. Unlike the Xenomorphs in the Alien franchise which are hard to kill, Sylvesters are very easy to kill (most likely due to being the first enemy encountered in that game).

Trivia

 * The Metroid video game franchise was highly inspired by the Alien franchise, and the villain Ridley from those games was supposedly based on the Xenomorphs, his design is very similar to a regular Xenomorph and his close combat attacks are quite similar to that of the Xenomorphs. Interestingly, the name "Ridley" is the same name that the creator of the Alien franchise has, which is Ridley Scott.
 * Another villain from the Metroid series that could have been inspired by the Xenomorphs is the Queen Metroid, but more specifically the Queen Xenomorph, as both are the queens over a species, and have similar appearances and traits.
 * A skull of Xenomorph can be seen in Predator 2 aboard the City Hunter ship, showing that Xenomorphs also exist in the Predator universe, though it is also likely just a shout out to the Alien franchise.
 * Given the dialogue in Aliens vs Predator (2010) from humans indicating that they have fought multiple Xenomorph infestations, and the Predators stating that they have multiple hunting grounds across the galaxy, along with the fact that the Xenomorphs have a natural home world in the ending of the Marine campaign, it is heavily implied that there are naturally occurring species of Xenomorphs out in the galaxy.

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