Let the Galaxy burn!
~ Horus Lupercal
Death to the false Emperor!
~ Codex - Chaos Space Marines Page 3.

Chaos Space Marines (also called Traitor Marines, Chaos MarinesTraitor Legionnaires and Heretic Astartes) is the term used to describe the many heretical Space Marines that betrayed the Emperor of Mankind and became servants of the Chaos Gods. They are part of what might be considered the more villainous race in the Warhammer 40k universe, alongside the Dark Eldar, Orks, Necrons and Tyranids, and part of the Forces of Chaos, which also include demons and lesser humans. Chaos Space Marines come in many forms and tend to have cults of both human and xenos followers. Depending on the philosophy of the legion, they are deeply devoted to certain chaos deities, either one or all of them, but on rare occasions none of them.

Unlike many other factions within Warhammer 40,000, rather than being united under the umbrella of a higher figure or as loosely affiliated groups, they are fractious, fickle, refractory and prone to infighting amongst themselves. They are only truly unified in their will to survive, hatred of the Emperor Of Man and their desire to help Chaos become the ruling power of creation via acts of unspeakable evil. Only when the Warmaster of Chaos (The current being Abaddon) launches a new temporary Black Crusade will the vast majority of chaos warbands unify, for the sole purpose of wreaking as much havoc and destruction upon the galaxy as possible, the Imperium in particular. 

They are a playable army choice in Warhammer 40,000 and also serve in a highly antagonistic role in the related media. Chaos Space Marines are the rough equivalent of Warhammer Fantasy's Hordes of Chaos.


Chaos Space Marines draw their origins back to the 31st millennium. Back then, eighteen legions of genetically modified super-soldiers, the Space Marines, fought to unite the galaxy under the banner of the Imperium of Man, in a campaign that history later called the Great Crusade. The Emperor of Man Kind claimed that the intention of this campaign was to unite humanity under one banner, wipe out any xenos that threatened their dominion or survival and establish humanity as the ruling force in the galaxy. In truth, however, the Emperor knew about the existence of the Chaos Gods and the dangers they posed. His secret agenda was to their install the principal of the Imperial Truth - an atheistic doctrine, which would turn humanity away from the elements that served as the Chaos Gods power source thus eradicating them once and for all.

Perhaps fearing the eventual result, Khorne, Nurgle, Slaneesh and Tzeentch, as well as the lesser gods of chaos stopped their own conflicts to interfere with the works of the Emperor of Man. The first step was to scatter his genetically modified children, the Primarchs across the galaxy thus ensuring that the Emperor could not raise or teach them under his own philosophy from an early age. As such each of the Primarchs would face his own trial and tribulations before the Emperor rediscovered them, which in some cases sowed the first seeds of resentment against their father.  

Only once the Great Crusade was already underway, would the Chaos Gods seize their chance. Starting with the Emperor's disenfranchised son, the pious Lorgar Aurellian, who became disillusioned with his father following an incident in which the Emperor publicly humiliated both him and his legion, the Chaos Gods seduced Lorgar into Chaos-worship. When the Primarch undertook a pilgrimage, they showed him horrifying visions of the future under the Emperor and convinced him that without the aid of Chaos humanity would share the fate of the Eldar. Having won over a powerful leader and orator into their cause, the Chaos Gods' campaign to subvert the Emperor's faithful soldiers had begun.

After purging his Legion of all elements with any loyalties left to the Emperor, Lorgar sent his First Captain Erebus as an ambassador. Erebus, keeping his Legion's new faith a close secret, began organizing the Warrior Lodges, secretive fraternal orders within the Space Marine Legions that existed outside of the Legion's regimented and ordered structures. Though these were under the guise of providing brotherhood without rank, they were instrumental in fomenting sympathies and paving the way for the coming betrayal.

Erebus proved instrumental for setting the stage to the Horus Heresy after seeding the Warrior Lodges into a full half of the Legions and successfully engineering the fall of Horus into Chaos by stealing a powerful weapon known as the Anathame and giving it to a rebellious planetary governor who injured Horus with it. Desperate to save their leader Horus' troops were tricked into bringing him to the serpent's lodge, a group of supposed mystical healers who unknown to them were secretly chaos worshippers. Using this opportunity the Chaos Gods managed to convince the injured Horus to turn against the Imperium in exchange for healing him and he quickly rose to power as the leader of the Chaos forces.

The resulting conflict stretched across the known galaxy all the way to the throne world of Holy Terra consuming billions upon billions of lives, devastating countless worlds and ultimately leading to the Emperor's permanent interment upon the life support system known as the Golden Throne. In the end though Horus' rebellion cost him his life and his fellow traitor troops were forced to retreat into the realm of the Warp through the dimensional rift known as the Eye of Terror in order to avoid the wrath of the vengeful Imperial forces. Never the less a new deadly enemy had been created, from amongst humanities own ranks.

After the Horus Heresy

For the next 10,000 years, the fractured chaos legions would periodically emerge from the warp to wage war against the Imperium. Their lives unnaturally prolonged and their bodies and minds twisted thanks to otherworldly energies of the Warp and the daemons that live there. In their most recent endeavor, the 13th black Crusade, the new Warmaster of Chaos Abbadon the Despoiler managed to destroy the Imperial Fortress world of Cadia, an event which allowed the energies of the warp to spill into the material world and quite literally split the Imperium and the galaxy at large in half. Imperial forces have since retaliated by launching a counter-crusade to push back the onrushing forces and seize the two remaining space paths to the other side of the galaxy, all while the chaos forces use the opportunity to harass and harry them as well as devastate any worlds in their path.

Known Chaos Legions

In the ten millennia that followed the Horus Hersey, hundreds of Space Marine Chapters have forsaken their oaths of loyalty to the Emperor, their Primarch and the Imperium. These new generations of Chaos Space Marines will often corrupt others, in exchange for the power and glory, promised by their new masters. However, thanks to the codex astrates, none of these chapters possess the military might of Horus' legions.

Generally however, the term is used to reference the nine First-Founding Legions and their Primarchs who first turned against the Emperor, thus dividing humanity for all of eternity. In the aftermath of the heresy, the majority of these legions were driven from real space into the Eye of Terror. There, the former allies fought endlessly with each other. Such was the devastating impact of this war, that many of these once might legions divided into roaming warbands. Like their loyalist kinsman, who broke into newly formed chapters, some of these traitor warbands adopted new names and philosophies to differentiate from their parent legion.

The following list comprises the known Chaos legions from the first founding: - 

The Black Legion

Legion number: XVI

Primarch: Horus - Warmaster of the Imperium, and later the First Warmaster of Chaos. The arch-traitor.

Primarch Status: Deceased - Horus was mortally wounded by the Emperor towards the climax of the Siege of Terra. Coming to his senses the Primarch begged for death, which was granted. The Emperor used his mighty powers to destroy his sons soul, thus ensuring that he could never be resurrected. After the Heresy, Fabius Bile attempted to clone Horus but none of his experiments ever matched the original. Abaddon the Despoiler personally killed the last clone of his gene-father. As part of the Sons of Horus' metamorphosis into the Black Legion, Abaddon ordered Horus' body to be destroyed, meaning that Horus can never be restored.

Current leader: Abaddon the Despoiler - Horus' successor, the Second Warmaster of Chaos.

Religion: The Black Legion are very open when it comes to their religion. Officially most follow Chaos Undivided, meaning that they polytheistic, worshipping all of the Chaos Gods. Noted to strike various pacts with demons and their patrons, astrates of the XVIth legion will give particular devotion to a single entity when the situation calls for it. That said, some of the legionnaires hailed from monothesitic legions and continue to revere one God. Their leader, Abaddon, is noted to be deistic. Although he does acknowledge the existence of the Chaos Gods, and will barter with these foul creatures, he does not truly worship any of them.

Additional notes: -

  • The XVIth legion was originally known as The Luna Wolves. However they changed their name to The Sons of Horus just before the start of the Heresy. When Abaddon later reformed the legion, he changed their name to their current one.
  • During the Dropsite Massacre at Istaavan III, nearly a third of the legion was labelled for extermination, as they were deemed to be more loyal to the Emperor than their Primarch. Once Horus and their brothers betrayal became apparent, these loyalists, under the leadership of Gavriel Loken cast off the iconography of Horus. In a further bid to re-affirm their loyalty to the Emperor they also readopted the title of Luna Wolves.
  • These are the most infamous of all the traitor legions.
  • The Luna Wolves power armor was originally white in colour. When they became the Sons of Horus, the astrates of XVIth legion repainted their armor dark green. This colour scheme was altered again, at the behest of Abaddon the Despoiler, who told his followers to paint their armor black with gold trimming. This was done to mask their shame of Horus' failure, and signify the legions rebirth.

The Word Bearers

Legion Number: XVII

Primarch: Lorgar - First of the traitor Primarchs.

Primarch status: Alive - Believed to be meditating deep within the depths of the Word Bearers new home world. Unconfirmed reports indicate possible sightings upon the ruined world of Cadia.

Current Leader(s): The Dark Council - A collection of Dark Apostles and Chaos Champions.

Religion: An eternally pious legion, the Word Bearers are staunch pagans of Chaos Undivided. They worship all of the Chaos Gods equally, never showing favor to a particular deity.

Additional notes: -

  • The legion was originally known as the Imperial Heralds but changed its name when Lorgar took control.
  • Once the Emperors most devoted followers, the XVIIth legion were the first legion to turn against the Emperor. They did this, following what they considered to be an unjustified humiliation and reprimand at the hands of the Emperor himself. When the existence of the Chaos Gods became known to them, many astrates willingly accepted embraced these new patrons, since the Chaos Gods welcomed their devotion, where the Emperor had spurned it.
  • Erebus, the Dark Apostle and Kor Phaeron, Lorgar's adoptive father were, chronologically, the first Chaos Space Marines ever.
  • Records suggest that prior to the legions fall, the Emperor threatened to purge Lorgar and the XVIIth unless they changed their ways. There is no indication that is threat inspired their eventual turn to Chaos, which was motivated by their faith more than anything else.
  • Before his fall, Lorgar penned the Lectitio Divinitatus, a book of reverence to the Emperor, which went against the Imperial Truth and argued about the Emperor's divinity. Ironically, this book gave rise to the Imperium's ecclesiarchy, and the modern-day Imperial Cult.

The World Eaters

Legion number: XII

Primarch: Angron - the Red Angel.

Primarch Status: Alive - Was last seen during the First War of Armageddon, where he was defeated but not destroyed. Unconfirmed reports indicate possible sights on Cadia.

Current leader(s): N/A, the XIIth legion has broken into various warbands, led by numerous champions.

Religion: The World Eaters exclusively worship Khorne, the God of Blood and War. They do not build places of worship or perform religious ceremony. The battlefield is their altar, with their victims serving as their offerings.

Additional notes: -

  • Were originally called the War Hounds, before the Emperor rediscovered Angron. The Primarch immediately renamed his new legion after his fallen comrades from the gladiatorial arenas on his homeworld.
  • They are some of the most formidable hand to hand warriors in the 40k universe, willing to fight anyone and everyone, including each other.
  • Their devotion to Khorne and their battlefield ferocity has earnt them the nickname, Khorne Berzerkers.

The Death Guard

Legion number: XIV

Primarch: Mortarian.

Primarchs Status: Alive - Mortarian returned to real space to initiate the Plague Wars. He dueled his former brother Roboute Guilliman at the climax of the conflict to a stalemate.

Current leader: N/A, the legion has fragmented and divided into warbands.

Religion: The Death Guard are the most adherents of Nurgle. Blessed by their deity to house plagues and diseases, they have mutated into what Imperial records now refer to as the Plague Marines.

Additional notes: -

  • Before Mortarian was found, the Emperor referred to the legion as the Dusk Raiders. Mortarian renamed them after his forces on his homeworld of Barabus.
  • Due to the mutations they have suffered as a result of Nurgle's blessing, the Death Guard and Imperium forces alike, refer to them as Plague Marines.

The Emperors Children

Legion number: III

Primarch: Fulgrim - The Phoenician.

Primarch Status: Alive - Confirmed sighting of Fulgrim on the planet of Istvaan III, where the loyalist elements of his legion perished. There the Daemon Primach fought and killed the Venerable Dreadnaught Rylanor, a loyalist survivor of his own legion. Left for areas unknown. Unconfirmed reports suggest possible sighting on Cadia.

Current leader: N/A, the Emperors Children legion has broken into warbands.

Religion: Slaanesh, the Dark Prince of Excess corrupted Fulgrim, and after that his legion. Where once they sought perfection in all things, the Emperors Children now seek carnal pleasure in all things.

Additional notes: -

  • The name of this legion, was granted to them by the Emperor himself. When Fulgrim reunited with the decimated remnants of the IIIrd legion, he gave a passionate speech of loyalty that moved everyone that heard it to tears. Amongst them, was the Emperor himself. So impressed was the ruler of mankind with Fulgrims devotion, that he gave the legion its title on the spot.
  • As a further reward for Fulgrims loyalty, the Emperor also declared that the Emperors Children had earnt the sole right to carry his personal symbol: the twin headed aquilla. Whilst later Space Marine chapters would universally incorperate this symbol into their armor, at the time of the Great Crusade, this was an honor reserved solely for the astrates of the IIIrd legion.
  • This was the legion that the profaned, amoral scientist Fabius Bile came from. Indeed, some of Biles earliest experiments were on his own legion. Bile eventually left the legion to continue his sadistic experiments without restraint.
  • Due to their extensive use of sonic weaponry, Emperors Children astrates are often referred to as Noise Marines.
  • Fulgrim holds the unique honor of being the only living chaos space marine primarch to have killed a loyalist primarch. In the betrayal at Istavaan V, Fulgrim dueled and personally killed his brother, Ferrus Manus, primarch of the Iron Hands. Later on, he also managed to "kill" Robute Guilliman shortly after the heresy. Guilliman was officially pronounced dead and locked in stasis, where he remained until his resurrection at the end of the 41st Millenium.
  • Unbeknownst to most, Fabius Bile managed to create a perfect clone of the pre-heresy Fulgrim. Despite Bile's best efforts, his experiment, later dubbed the Phoenician Clone, was noted to display loyalist affiliations. Left with no choice, Fabius eventually betrayed his creation. Currently, The Phoenician Clone is imprisoned within the Necron Lord Trazyn the Infinite's extensive collection. In exchange for his new prize, the collector gave the scientist thousands of Emperors Children gene-seed. 

The Thousand Sons

Legion number: XV

Primarch: Magnus the Red.

Primarch Staus: Alive - Fought Guilliman on Luna, now heading an invasion force in the Stygius Sector.

Current leader: Various, several known bands exist.

Religion: As prominent magic users, it did not take long for the Thousand Sons to find favor with Tzeentch, the Changer of Ways.

Additional notes:-

  • The legion was left with no choice but to side with Chaos when Magnus broke a sacred taboo to warn the Emperor about his brother Primarchs betrayal. The Emperor sent the Space Wolves to orgiinally bring Magnus in for questioning, but Horus tricked Lemun Russ into thinking this was an order of extermination. Magnus pledged his warriors souls to Tzeentch and since then they have followed him without question.
  • Following the Rubric of Ahriman, most of the legion has been transformed into bodiless automatons, whose souls are now eternally bound to their power armor. These undead warriors are now known as the Rubric Marines. 

The Iron Warriors

Legion number: IV

Primarch: Perturabo.

Primarch status: Alive - current location unknown.

Current leader: N/A, a civil war divided the legion creating various warbands.

Religion: Imperial records classify the Iron Warriors as being part of Chaos Undivided. This means that astrates of the IVth legion, should worship all of the gods to varying degrees. In reality however, the Iron Warriors are materialists that favor the gifts of science and technology. Indeed, they are noted to openly despise magic in any shape or form. Whilst the Iron Warriors do acknowledge the existence of the Chaos Gods, they do not actively worship them. This is because, like their Primarch, astartes of the IVth legion hold little attachment to anything, including faith. As such they are better described as being either agnosts or deists.

Additional notes:-

  • Although they seek conquest in all its glory, and show no mercy to their enemies, the Iron Warriors have been known on very rare occasions to aid the forces of the loyalists against overwhelming odds.
  • In accordance with their materialist philosophy, Iron Warriors are noted to rarely work alongside demons or other entities of the warp. Daemon Princes are likewise quite rare within this legion.
  • Such is the Iron Warriors hatred of chaos blessings, that if an astrate shows any signs of physical mutation he will be assessed. If the corruption is deemed too great and irreversible, the soldier will be terminated. If on the other hand, the legionary is deemed salvageable, the affected tissue/limb will be amputated. The warrior will then receive a cybernetic replacement.

The Night Lords

Legion number: VIII

Primarch: Konrad Curze - The Night Haunter, the most feared and mentally unstable of any of the Primarchs.

Primarch status: Deceased - Curze allowed himself to be killed by an Imperial Assassin, shortly after the Heresy. Throughout his life, Curze had received frequent visions of his eventual demise. He believed that by not countering it, he proved that everything he had done was predestined.

Current leader: N/A. the legion broke apart in the aftermath of Curze's death and has since divided into several warbands.

Religion: The Night Lords are officially classified as being part of Chaos Undivided. Similar to the Iron Warriors, in reality, the Night Lords regard of religion is much more complicated. In fact, they represent a thus far unique case, which makes them an oddity, even amongst the Chaos Space Marines. Unlike the rest of their traitor kinsman, who follow the gods of Chaos to varying degrees, astartes from the VIIIth legion do not acknowledge or worship Khorne, Nurgle, Slaanesh, Tzeentch or any of the other entities at all. On the contrary, they have been known to actively mock their brethren for their loyalties to the immaterial.  Instead, the Night Lords are dedicated to Curze's principals of fear and terror above all other things, with their actions aiding the cause of Chaos as a side-effect. Despite evidence to the contrary existing all around them, the Night Lords, for the most part, appear to be staunch atheists.

Additional notes:-

  • The Night Lords are regarded as one of, if not the darkest Space Marine legion that was ever created. Even during their tenure as loyalists, the VIIIth legion had a fearsome reputation for brutality and savagery. Many worlds surrendered to them freely in the Great Crusade and afterwards rather than face their wrath, only to be exterminated anyway.
  • Autopsies carried out on post-heresy Night Lords has shown that their gene-seed has changed little if at all, when compared to their pre-heresy kin.
  • As a result of their lack of devotion to Chaos, Daemon Princes and demonic summoning is the exception, rather than the rule within the Night Lord legion.
  • The Nights Lords where the first legion to officially leave the Emperor's service and turn renegade. This happened prior to the Horus Heresy, though, when the conflict began, they did pretend to return to the Emperors service only to switch sides, and join of Horus.

The Alpha Legion

Legion number: XX

Primarch: Alpharius Omegon - In a unique case, the Alpha legion had two Primarchs, the twins Alpharius and Omegon. The two brothers considered themselves to be two bodies with one soul.

Primarch status: Unknown. Rogal Dorn, Primarch of the Imperial Fists, duelled and killed one of the brothers above Pluto, reportedly Alpharius. Roboute Guilliman is generally believed to have killed the other Primarch after the Heresy, but this remains unconfirmed.

Current leader: Unknown. Various warbands exist, but given their secretive nature it also possible that the entire legion answers to a hidden overlord.

Religion: Famed for their use of cultists, the Alpha Legion worships Chaos Undivided.

Additional notes: -

  • The Alpha legion are one of the few legions that did not move towards the Eye of Terror after Horus' defeat. Even today, they maintain an ongoing presence in real-space.
  • The twin Primarchs, Alpharius and Omegon, were both noted to be very small when compared to the rest of their kin, at around the same height as a Space Marine Terminator. This is one reason that nobody can say for certain whether or not the leaders of the XXth legion have truly been vanquished.
  • Alpharius was confirmed as the Primarch slain above Pluto and thus is truly dead. Sensing the death of his twin, Omegon took up the title Alpharius Omegon, to sow confusion amongst his enemies. His eventual fate, is much more disputed.
  • Despite being part of the Forces of Chaos, evidence from various sources indicates that the Alpha Legion (or at least the first generation) may in fact be covert operatives. Prior to his "fall" Alpharius received a vision in which he saw the twin fates of the galaxy. In one version, the Emperor won the Heresy but Chaos ultimately triumphed as a result of the subsequent turmoil. In the other vision, Horus defeated the Emperor but then lead humanity to the point of extinction, resulting in the death of the Chaos Gods. After receiving his visions, Alpharius is reported to have said "Whatever I do now, I do for the Emperor!"


Community content is available under CC-BY-SA unless otherwise noted.