They are named after Seven Deadly Sins from Christian doctrine.
In the original manga and the Brotherhood version, the original Homunculus is a mysterious being created from the blood of Van Hohenheim. For the beginning of his life, he was kept inside a flask, having no real solid form to assume. He appeared as a black, shadowy orb with one large eye and a very wide smile. Forming a friendship with Hohenheim, Homunculus granted the man knowledge of various academics, including math, science, and alchemy. King Xerxes, the leader of the region where Hohenheim lived, strongly desired immortality, and commanded Homunculus to explain how to achieve immortal life. Homunculus instructed him to form a transmutation circle around the country, with a large massacre at every point. King Xerxes followed the directions of Homunculus, and was, then, instructed to stand at the center of the transmutation circle, where he would receive his immortal body.
However, Homunculus tricked Xerxes into standing away from the center, where Xerxes was killed. Homunculus, smiling, looked up at Hohenheim, who was holding his flask, and told him that he and Hohenheim were standing at the true center of the transmutation circle. Everyone in the region was killed, except for Hohenheim and Homuculus who both received immortal bodies formed by the souls of the people who had been sacrificed. Hohenheim, horrified by what Homunculus had done, left Homunculus, vowing to kill him one day. Homunculus in the meantime, became Father and would create other homunculi in his plot.
Manga and BrotherhoodFollowing suit, the Homunculi that appear within the manga and Brotherhood are the creations of Father, allegedly to purge himself of his own sins so as to ascend to a godhood state upon The Promised Day. These Homunculi are created using the various souls within himself to construct Philosopher's Stones, making the Homunculi relatively immortal until their Stones are worn. However, such sins are still present within Father as seen through his Homunculi.
- Lust: Desire for power and willingness to manipulate others for it.
- Gluttony: Consumption of resources at his disposal, such as the fate of the first Greed.
- Envy: Envy of humans for their ability to have families and create meaningful bonds-Hohenheim explicitly refers to this as his reason for creating the Homunculi.
- Greed: Aforementioned desire for power.
- Sloth: Having others do the work while he resides underground and directs.
- Wrath: His anger in general, but particularly notable in his confrontation with Hohenheim.
- Pride: Father's superiority complex, such as seeing humans as ants.
While serving as antagonists as in the manga, the Homunculi of the 2003 anime are created through a different means. They are the result of an alchemist attempting human transmutation to resurrect a dead individual, costing them portions of their own bodies and creating a horrific being in the process. When the results of these transmutations are fed Red Stones, they gain a shape reminiscent of the human target of the attempted resurrection. Two particular examples are Sloth and Wrath, created from the Elric Brothers' and their teacher Izumi Curtis' attempt to bring back their mother and infant son respectively. Another is Lust who, in this incarnation, was the result of Scar's brother trying to bring his lover back. Due to this imbalance, Homunculi are weakened in the presence of any artifact of the original resurrectee's corpse.
The 2003 anime Homunculi serve as the lieutenants of Dante in her efforts to create another Philosopher's Stone to continue her immortality and body-hopping. Dante created several of them, eventually gaining Lust, Sloth, and Wrath in League with her after the three are fed red stones. As aforementioned, they are relatively immortal until exposed to the remains of the resurrectee, which will weaken them enough to be killed.
Dante actions and her relationship to the homunculi are similar to Father in the manga:
- Envy - Her jealousy of Hohenheim choosing to spend the rest of his life with Trisha Elric.
- Greed - Her goal to obtain the Philosopher Stone, which will allow her to cheat death.
- Gluttony - Her aforementioned desire for the stone's power.
- Pride - She has an air of superiority when around others.
- Lust - Her act of swapping bodies can be considered an act of "violating" her victims, she chooses the most beautiful bodies to steal and has made several advances towards Hohenheim (implying that they sleep together). She was going to use Rose's body and be loved by Edward Elric (the son of Hohemheim).
- Wrath - She can be unforgiving towards those who get in the way of her plans, such as her homunculi legion and even her former-lover Hohenheim.
- Sloth - Dante often has her subordinates do the footwork for her.
Other Homunculi-like creatures serve as antagonists in the series. Most notable are the Mannequin Soldiers created through bonding the Philosopher's Stone's various souls to the bodies of humanoid monsters. It it theorized that they are created to serve as an additional Philosopher's Stone source for Father.
- All of the named Homunculi die in a way related to the sin they 'embody':
- Lust was incinerated to death by a man well known as a serial dater, who 'lusts' after the position of leader of Amestris.
- Greed was boiled down for his most valuable part, and later killed again for the same part by Father.
- Gluttony was devoured by Pride.
- Envy commits suicide out of jealousy and self-loathing toward humans.
- Sloth wears out from his Philosopher's Stone during a long fight.
- Wrath has his arms dismembered by one of the vengeful people he tried to exterminate.
- Pride was stripped of his power and had been reduced to the form of one of the creatures that he despised.
- Father while not named after a sin, was largely undone by the efforts of Van Hohenheim, the one from whose blood he was "born", and Greed, his own son.
- Though a bit of a stretch, the finishing blow was dealt by Edward Elric, who could also be considered his biological son because he is more or less a clone of Hohenheim.