In Fullmetal Alchemist: Brotherhood, Envy is one of the seven homunculi, artificial humanoids created by the being known as Father. Envy personifies the sin of jealousy and was created when Father extracted this specific emotion from himself. As a homunculus, Envy possesses a core of Philosopher's Stone energy, which grants immortality and regenerative abilities, but this core also serves as a critical weak point. The Ouroboros tattoo, the symbol of the homunculi, is located on Envy's outer left thigh.

In terms of appearance, Envy most frequently takes the form of an androgynous, youthful individual with an effeminate face, sharp features, and dark hair with subtle green undertones. This form is lithe and of modest stature. Envy is canonically genderless, a reflection of being an artificial being rather than a born human, and prefers this particular shape. When provoked, significantly damaged, or wishing to display power, Envy sheds this humanoid guise to reveal a colossal, monstrous true form. This beast is a nightmarish, reptilian creature of immense size and strength. Its body is grotesquely covered in the writhing, melting faces and torsos of the thousands of souls that comprise its Philosopher's Stone core, the lingering residue of the destroyed nation of Xerxes. The transformation is deliberately horrifying, visually representing the mass of human suffering that fuels Envy's existence. When the Philosopher's Stone is nearly exhausted, Envy cannot maintain even this monster state and reverts to its most vulnerable appearance: a small, pathetic, worm-like creature with little power.

Envy's personality is defined by cruelty, sadism, and a profound contempt for humanity. Envy delights in psychological torment and views humans as foolish, weak, and easily manipulated pawns. This is not merely a means to an end but a source of genuine, mocking pleasure. Envy is a master of emotional warfare, preferring to inflict maximum anguish before delivering a killing blow. A signature tactic involves shapeshifting into a victim's loved one to create hesitation and betrayal, as demonstrated when Envy murdered Maes Hughes by first taking the form of his wife. Beneath this arrogant and smug exterior, however, lies a core of deep-seated self-loathing and loneliness. Envy’s entire identity is built on a fundamental jealousy of humanity’s resilience, emotional bonds, and ability to persevere through failure. The homunculus mocks these traits publicly while secretly resenting that it can never truly possess them.

Envy’s primary motivation is to serve Father’s grand plan to sacrifice all of Amestris to become a god. As a field agent, Envy carries out missions that require infiltration, deception, and assassination. The character’s most devastating act was single-handedly sparking the Ishvalan civil war. Decades before the main story, Envy disguised itself as an Amestrian soldier known to be a moderate who publicly opposed the military’s occupation of Ishval. In this form, Envy shot and killed an unarmed Ishvalan child, igniting the massacre that would consume hundreds of thousands of lives. Envy later brags about this atrocity with pride, noting with satisfaction that the real officer was court-martialed and executed for a crime he did not commit. Later in the narrative, after the homunculus Lust is killed, Envy expresses genuine anger and grief, revealing that despite a facade of indifference, the homunculi do share a twisted sense of kinship. Envy’s central relationship with the protagonist Edward Elric is complex. While primarily antagonistic, Envy seems to hold a specific, mocking fondness for Ed, often taunting him directly. In their final confrontation, Edward refuses to kill the helpless, worm-like Envy, instead expressing pity and understanding that Envy’s cruelty was always a mask for its jealousy of humans. This empathy, offered by a human child, is the ultimate insult to Envy, who chooses to tear out its own Philosopher's Stone core and commit suicide rather than accept pity or admit the truth of Edward’s words.

As a shapeshifter, Envy’s primary ability is to assume the appearance, voice, and mannerisms of any person or creature. This power is used for espionage, framing innocents, and psychological torture. In its humanoid form, Envy possesses enhanced speed, agility, and strength beyond a normal human. When enraged or fighting seriously, Envy transforms into the giant reptile monster, which possesses tremendous physical power and can also morph its limbs into weapons like blades. While powerful, this form is also a liability, as it consumes large amounts of the Philosopher’s Stone’s energy. Envy’s ultimate weakness is the Philosopher’s Stone core itself. If the stone is depleted or deliberately destroyed, Envy loses its regenerative powers and reverts first to the monster form and then to the helpless worm state. Prolonged exposure to flames, such as those generated by Roy Mustang’s alchemy, can rapidly burn through the stone’s energy reserves, forcing Envy into its most vulnerable state.