Envy

Envy (Japanese: エンヴィー Envi) has the ability of shape-shifting. He uses this power to assume the form of any person and even copy their voice.

Envy was most comfortable in the "adorable" and "beautiful" form of a androgynous teenager. He usually serves as a spy, but, sometimes, his abilities are really useful to assassinations, such as when he killed Maes Hughes. Envy's most used technique to kill humans is to impersonate someone the target loved or cared, and use their hesitation as an opportunity to kill them. Envy is not as smart as Lust, Pride or Wrath but is by no means an idiot. In fact he can be just as good a puppet master as Lust. But this is overshadowed by his cockyness and bad temper. His temper can easily be set off by insulting his large and delicate ego causing him to make mistakes

The Reasoning by his name Envy is not that he envy's the humans, but the fact he can change into any form

In the anime
Envy is first seen at the end of episode 2 of the 2003 series, where he starts to impersonate the tarnished Father Cornello. Envy is not seen in his preferred form until the beginning of episode 14, and he does not reveal his original form until episode 50. As the oldest Homunculus, Envy claimed that he had forgotten what he originally looked like; this was a lie stemming out hatred for his "father", Hohenheim. This was because Hohenheim was the one who created Envy, trying to bring back his first son (who died of mercury poisoning around the age of eighteen). Envy hated all humans and followed Dante mostly for the opportunity of killing as many people as he could. This was what drove Envy in all that he did; unlike other Homunculi, Envy did not care about the Philosopher's Stone, nor about becoming human. His most prominent murder was that of Maes Hughes: after his cover was blown while he impersonated Second Lieutenant Ross, Envy transformed into Hughes' wife Gracia, using Hughes' hesitation to fatally shoot him. Envy was also key in imprisoning Greed, against whom he had a long-standing grudge, within the 5th Laboratory. It is notable that Envy had no love for his homunculi brethren, antagonizing his first "brother", Greed, and quickly turning upon Gluttony, Wrath, and even the higher ranked Pride. The only character that posed the possibility of a relationship with Envy was Dante herself. Envy was usually Dante's enforcer, carrying out her whims more directly than most of the sins, and he was apparently more comfortable in her presence than the others. However, Envy also lashed out at Dante with particular intensity when she impeded his ambition of death and revenge. Well aware of the power that Dante held over him, Envy was at once the most uncontrollable and the most reliable member of Dante's legion.

Envy's true form, from "Death". It is revealed in the penultimate episode of the 2003 series that Envy was created four hundred years ago by Hohenheim in an attempt to resurrect the son he and Dante had, who had died from mercury poisoning when he was eighteen years old. Envy held a great hatred toward Hohenheim for never being acknowledged as his son and for abandoning him and Dante. As a result, he also hated his younger "half-brothers" Edward and Alphonse as they obtained the fatherly love that Envy himself never received. When learning from Dante that Hohenheim was gone, Envy snapped at being denied his wish to kill him. The fact that the Elrics possessed the stone and would gain back all that they had lost made Envy more "envious" of the Elrics and on making them suffer as he had. However, Edward managed to see through Envy's disguises and tricks until the Homunculus revealed his true form (an imitation of Hohenheim's deceased son with Dante) and his connection to Hohenheim. That stunt was all it took for Envy to successfully kill Edward, as the distraction gave Envy enough time to pierce Ed through the heart. Envy is then transported to the gate by Alphonse, meeting up with Edward again. Upon learning Hohenheim still alive on the other side of the Gate, Envy was able to successfully open and make his way through the doors. Once inside the gate, the creatures attacked him, but he fought them off by transforming into Edward, then, just before finishing his demand to see his father, he changed once again into his original human form, probably as a way to get the creatures in the gate to take him to Hohenheim faster, which might explain the Edward transformation. By the time he made his way through to the other side, Envy became a serpentine dragon.

During the two year gap between the end of the TV show and the movie, Envy was captured by the Thule Society. With Envy in his massive serpent form, the Society intended to use Envy as a literal Ourobouros to open a physical Gate and transfer their soldiers to the other side, to "Shamballa". Hohenheim was imprisoned and offered to Envy as a sacrifice; a human chew-toy to keep the "Great Snake" calm as they formulated their plans. Around the time of Fullmetal Alchemist the Movie: Conqueror of Shamballa, Envy escaped and took shelter in an abandoned castle, only to cross paths with Edward once again. In their ensuing fight, Envy was attacked on all sides by the Thule Society, who recaptured him and managed to get a small regiment of soldiers to the other side for a short time. In the end, it was Hohenheim who took his own life using Envy as his means, enabling Ed to return to his own world in a final act of redemption for his sins, using Envy as material to create a gate between the two worlds.

In the manga
Envy was the fourth Homunculus created by Father, though often referred to as a 'he' Envy is apparently genderless and can take almost any form it chooses. Referred to by Lust as the most cruel or sadistic of the Homunculi Envy shows the most open disdain of humans and relishes in any opportunity to hurt, humiliate, or insult them. It is also quite vain and short tempered and dislikes anyone insulting his appearance. Beneath this cruel exterior however Envy is secretly envious of humans' inner strength and the mutually beneficial friendships that they share, since most of the Homunculi show little real concern or emotional support for each other.

In addition to the standard regeneration, longevity, and apparent immortality of the Homunculi, Envy can also shift his form into anyone or anything, even changing parts of itself into multiple different being or objects simultaneously. Although already formidable in human form it can assume a much larger monstrous shape with a long tail, elongated face, long black mane, four arms and four legs, and a multitude of human bodies and faces protruding from its flanks and shoulders. These are physical representations of the dozens of souls of Xerxes within its Philosopher's Stone, all saying independent things which Envy uses to distract and unnerve it's opponents. However Envy can only change its size and shape but not its mass, therefore it weighs much more than a normal sized being and often creates cracks or deep impressions in the ground that are easily followed.If it suffers too much damage Envy can reduce itself to a tiny parasitic lizardlike form resembling a fetal shape of its full sized body. In this state it can merge with and control other organic beings, in the case of lesser homonculi (i.e. Father's artificial soldiers) it can absorb them and their Philosopher's Stones completely reforming its original body.

Envy operates mainly as a assassin and manipulator, using its shape-shifting abilities to impersonate and manipulate unsuspecting humans. Parading as a State soldier, it shot the Ishvalan child that started the uprising which lead to the Ishval massacre. While masquerading as 2nd Lt. Maria Ross it also shot and killed Lt. Col. Maes Hughes when he discovered the secret of the founding of Amestris, an act with earned him the unknowing hatred of Roy Mustang. After Lust's death he replaced her as Father's messenger.

Envy's true form was first revealed when it, Ed and Ling Yao were all swallowed by Gluttony, who was in a rage knowing that Roy Mustang, the killer of Lust, was near. Thinking that the situation was hopeless, Envy figured it would do no harm and it could have a bit of fun. Envy almost killed Ed, swallowing him alive, but then Ed saw the Philosopher's Stone at his core, giving him an idea. Ed managed to placate the monstrous Envy and let it allow him to use it's Philosopher's Stone to open Gluttony's fake Doors of Truth to pass through the true doors back to the real world. This drained many of the souls from Envy in the process, but evidently not enough to kill it.

Envy later released Zolf Kimblee from jail and asked him to work for the Homunculi, giving him an extra Philosopher Stone to supplement the one he had kept since the Ishval Massacre. Later, the chimera Zanpano pretends to betray his comrades to lead the Homunculus into a trap and Tim Marcoh succeeds in destroying most of the souls in its Philosopher's Stone, reducing Envy to its tiny parasitic form. After an unsuccessful attempt to hold Yoki hostage, Scar gives it to Mei Chan and tells her to bring it to the Xingese Emperor. Yet Envy convinces her to bring it back to Central instead by telling her to help her friends. There, it directs her into Father's subterranean lair where it frees itself from the bottle and absorbs enough lesser Homunculi to return to its normal state.

Soon after Envy is confronted by Mustang, revealing to him that it was Hughes' murderer. The two begin a ferocious battle, however Envy is at a huge disadvantage since its new body is highly flammable, and the revelation drives Mustang into a furious desire for revenge. Envy attempts to catch Mustang off guard by transforming into Hughes, but this only enrages Mustang further. After fleeing again, Envy makes an attempt on Riza's life, but is quickly found out and shot repeatedly with her many weapons; though Envy does manage to catch hold of her, Mustang reappears and continues the decimation of Envy's new body till its reduced back to its parasitic form again.

Envy is saved from execution by Mustang's hands through the combined actions of Riza, Scar and Edward, in order to cease Mustang's quest for vengeance. After unsuccessfully trying to tempt the group into fighting each other, Envy is enraged and dumbfounded by how former enemies can put aside their hatred and work together. Edward then suggests that Envy is in fact jealous of human friendships and ability to support each other. Moments later a tearful Envy commits suicide by pulling out and crushing its own Philosopher's Stone, ashamed that only Ed knew how he truly felt. As his decaying body fades away, he whispers 'Good luck' with tears in its eye. Envy was the third Homunculus to die.

Trivia

 * Interestingly, it is revealed in the game Fullmetal Alchemist: Dream Carnival, that Envy enjoys chocolate parfaits.
 * Envy's last words in episode 51 the last episode of Fullmetal Alchemist: "Like hell there isn't! I'll tell it exactly where to take me! (opens the doors of the Gate) I've come to kill him! Take me to Hohenheim of Light! (enters Gate, black babies attach themselves to Envy) Stop messing with me! You'll do as I tell you! (Transforms into Edward Elric) You're taking me to see Hohenheim! To that bastard! (Transforms into his original human form) TO MY FATHER!" (Transforms into a Serpentine Dragon).