Envy was one of seven homunculi born from Father, the first homunculus created in the world; Envy, along with the others, each represented the embodiment of one of the seven sins carried within each human, which Father wished to purge himself of. Not only were the name of each homunculus representative of their respective sin, but so were their powers and personalities. All of the homunculi were expected to assist Father in his various goals: building up the Amestrian government, finding suitable human sacrifices, manipulating and killing humans wherever and whenever necessary, and generally serving their father without question or hesitation.
The unique aspects of Envy included its primary power: the ability to transform its body to perfectly imitate any human or animal. Although mistakes in the imitation can be made if Envy is not observant enough of the individual it is mimicking, these accidents are rare-it happens only once in canon. Another aspect unique to Envy is its genderlessness: unlike Lust, who is female, and the other homunculi, who are either definitely or very likely male, Envy possesses neither a distinct gender nor a combination of genders in its default form, making it effectively genuinely genderless.
Because of the unique qualities and abilities given to them by Father, each homunculus was given suitable duties. Envy was given assignments fitting for one with the ultimate disguise: reconnaissance, infiltration, confounding enemies, and assassination; Envy also doubled as a mediator and informer between the homunculi and their subordinates across Amestris. The two most prominent and memorable examples of Envy’s skills being executed are its assassination of Lieutenant Colonel Maes Hughes and initiating the Ishvalan Purge, both of which it used its wits and disguises to pin the blame on innocent individual humans.
Unlike most of its siblings, Envy did not carry out its missions out of dedication towards Father. Rather, it did so due to the combined factors of being too terrified of Father to object to anything and greatly enjoying torturing, humiliating, and killing humans, giving it little reason to object to any of Father’s orders; the extent to which Envy enjoyed creating misery and pain amongst humans was enough that the other homunculi came to label it as “the cruelest homunculus”, which, considering that most of all the homunculi could be argued to be quite cruel, was quite a statement, which Envy came to be proud of.
However, this pride was simply a mask of denial. After several humiliating defeats, it became obvious that Envy possessed very, very severe insecurities; after its first defeat at the hands of an old alchemist doctor it had, up to that point, manipulated cruelly and several chimeras, Envy screamed and shouted in the most pathetic and humiliating fashion possible; it could not stand to see itself humiliated and defeated but, more importantly, the sight of the humans and chimeras looking down on it-a creature that was supposed to be superior to them-tore into its pride; this became all the more worse because the expressions of hate and fear the others had just moments prior had turned into expressions of pity for Envy, which agonized it far beyond the pain of its physical wounds.
Despite its constant gloating-claiming to be better than humans, calling itself “the great Envy”, and laughing at the misfortune of those it tricked-Envy was, in fact, a very, very insecure individual. When not in control of a situation-which was, admittedly, rare due to its manipulative abilities-Envy would lose control of itself and panic; when at the complete mercy of an opponent, Envy would plead, beg, and literally, genuinely cry; when looked upon with pity rather than hate or fear, Envy would react with abject horror; when called simple insults such as “ugly”, Envy would react with absolute contempt and fury. Despite the show of pride and arrogance, Envy was actually a being with no pride that was perpetually moments away from breaking down and crying.
Envy lived up to its name: the insecurities and frustrations it possessed were the direct result of its own jealousy towards humans. It saw the various sorts of relationships humans were capable of having with one-another as something it did not and could not have; unlike most of its siblings, Envy saw that the ‘family’ it was a part of was nothing more than a poor imitation of the ones humans had and knew the allies it had-the other homunculi as well as the humans serving them-were not the same as the friendships humans were capable of having; it recognized the strength and fortitude humans were capable of possessing as a result of these relationships and knew fully well that it itself was weaker because of what it lacked. It were these jealousies that fueled Envy’s hatred of humans and were the reasons for its entire motivation for being so cruel and taking so much pleasure in the suffering of humanity: only by crushing those it wished to be more like could it continue to live in denial of its own inferiority. The fact it did so via taking advantage of those relationships that it envied so much was not a coincidence/
In the end, this had all come to light thanks to the insight of Edward Elric. After having been defeated soundly and completely by Roy Mustang and Riza Hawkeye to avenge the death of Maes Hughes-a kind man who had befriended many other people and had been murdered by Envy-its life was literally in the hands of the Fullmetal Alchemist. In a last ditch effort to prevent itself from being fully humiliated, Envy attempted to pit its enemies against each other by pointing out various reasons they should not trust one-another, but it fell on deaf ears. While most ignored its shouting, only Edward Elric saw past the attacks on their relationships to the motivating factor as to why Envy behaved that way and told Envy, in a voice of genuine concern and surprise, that it was envious of humans and their relationships.
This had been the first time in its two hundred year life that another being-human or homunculus-had pinpointed the core of Envy’s whole being and saw its most humiliating and well-kept secret. With its secret out in the open and incapable of shielding itself with denial, Envy admitted the truth to everyone present, including itself. Its secrets exposed, it defeated, and it having no more motivation, Envy crushed the Philospher’s Stone that acted as its heart, killing itself. In its final throes of life, Envy cried, wished the humans luck in defeating Father, and, for the first time, called Edward Elric by name.
Upon waking in Mayfield, it assumed much to its surprise to be in Hell, where it belonged. It had been more than willing to accept the circumstances and was, in fact, content until it encountered Ed Elric once again. It had despaired upon realizing it was not in Hell and that it could not opt for death. To this day, it believes itself to be incapable of and disallowed from having those relationships it had envied for so long; however, due to its façade being broken and the Fullmetal Alchemist present, Envy is cultivating this jealousy inwardly as frustration and disappointment rather than externally as violence and hatred. It still has yet to realize that being a homunculus does not condemn it from eventually having what it envies.