Envy

(Japanese: エンヴィー Envi) has the ability of shape-shift. 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 assasinations, like 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 a opportunity to kill them.

In the anime
Envy is first seen at the end of episode 2, 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 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.

Interestingly, it is revealed in the game Fullmetal Alchemist: Dream Carnival, that Envy enjoys chocolate parfaits.

Last Words: 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).

In the manga
The fourth Homunculus created by Father, the dry and effeminate Envy has the ability to take on any form it chooses.

As it likes to brag, Envy, parading as a State soldier, shot the Isvaran child that started the uprising which lead to the Ishvar massacre. He also, masquerading as 2nd Lt. Maria Ross, shot and killed Lt. Col. Maes Hughes when he discovered the secret of the founding of Amestris. His ability to shapeshift is an excellent tool for assassination.

Envy was created from tens of thousands of the souls Father took from Xerxes. His true form is giant monstrous beast with a Philosopher's Stone at it's core, all the souls of Xerxes sticking out all saying independent things which Envy uses to distract and unnerve it's opponents. The one weakness of this skill is that he can only change the outside and not the mass of his form, meaning if he had to escape someone with a good eye could check the ground to see cracks, sunken ground, ect.

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, 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 Amestris. This drained many of the souls from Envy in the process, but evidently not enough to kill it.

After Lust's death he replaced her as Father's messenger. He released Zolf Kimblee from jail and asked him to work for the Homunculi, giving him two Philosopher's Stones. Later, the Boar-Chimera Zampano pretends to betray his comrades to lead him to a trap and Tim Marcoh succeeds in destroying his Philosopher's Stone, reducing him to a bug-sized creature. After an unsuccessful attempt to hold Yoki hostage, Scar gives him to May Chang and tells her to bring him to the Xingese Emperor. Yet Envy convinces her to bring him to Central instead. There, he led her in Father's subterranean lair where he managed to get free of his bottle an absorb enough lessers Homunculi to return to his normal state. He and May are engaging a fight.