Lust/2003 Anime

Lust is the first Homunculus formally introduced in the 2003 anime adaptation of Fullmetal Alchemist. (although technically not the first witnessed by the Elrics, chronologically). She is largely the same as her manga counterpart, however, she begins to crave becoming a human as the series progresses.

Her main purpose amongst the Homunculi is gathering information and traveling abroad, manipulating alchemists into creating Philosopher's Stones (her work can be seen for what it truly is in her dealings with Cornello, Mugear, Lujon, and others). Gaining true humanity is the focal point of her ambition, arguably much more so than the rest of the Homunculi.

History
Lust claims to have first observed the Elrics while she was evaluating the potential of the alchemist Majhal to create a Philosopher's Stone. While she was always in the background, using those like Cornello or Mugear, Lust only revealed herself to the Elrics years later during the events of the 5th Laboratory, where she attempted to convince Ed into creating a true Philosopher's Stone. Lust doesn't introduce herself or Gluttony by name to Edward until they met face to face again in Lior. Even then, she only introduces herself intending to kill Edward immediately after.

She is often directly involved in encouraging humans to seek out the Philosopher's Stone, using their desire for the stone to her advantage. Once baited, the alchemists are molded into following whatever path that best suits Lust and the other Homunculi's designs. She also tends to be more involved with the intrigue side of various conspiracies. Lust was created by Scar's brother, when he attempted to use alchemy to bring his lover back from the dead. After he was cast out from Ishvalan society as a heretic, Envy visited the wretched creature and fed it red stones, giving her human shape, and her new name. She was not the first Homunculus to bear the name of Lust, and is the third youngest Homunculus, only Wrath and Sloth are younger.

While ruthless throughout most of the series, she changes near the end during the Lior incident as she begins to recover some memories of her life as a human, and she softens particularly towards Scar and the Elrics. But her involvement was reckless, and allowing the Elrics' escape–a locket containing strands of hair from the woman she "was" prevented her from action–raised doubts about her loyalty. Lust was taken to Dante, who gave her a chance to redeem herself by helping Wrath take out Edward while Sloth abducted Al. Finally realizing Dante's true intentions were never to make the Homunculi human, Lust defected from the Homunculi. After at first trying to kill Ed, Lust betrays Wrath and forms an alliance with Ed under the condition that he help make her human. In return, she would reveal to the Elrics the identity of her master. However, to save Sloth from the ambush Edward and Lust set up for her, Wrath uses the locket and the transmutation circle that Lust made for Edward to use on Sloth, immobilizes and kills her by transmuting his arm temporarily into a blade. Before her death, Lust wonders where she will go when she dies. As if the whole reason she wanted to become human so badly was so she could die and, ironically, her question is answered. She is the second Homunculus to die in the anime.