Father

The being's earliest shape, sealed in the flask, is a small sphere of black gas with one eye, a wide toothy grin, and reaching tendrils, an image that mirrors the Eye of Truth beyond the Gate, the source he was drawn from. In that state he cannot work alchemy himself and would perish outside the glass. His second body is a near-double of Van Hohenheim, differing only in coloring and a few small details; Hohenheim calls it a hollow husk masking the real thing. Seated on a Philosopher's Stone throne deep below Central, he channels his Stone through pipes across Amestris to switch off the nation's alchemy whenever he likes.

Because his frame is built from a Stone holding half the souls of Xerxes, he can create and swallow Philosopher's Stones and cast alchemy without any circle, clap, or motion. Later he sheds the husk for a shifting, amorphous form studded with red eyes, and after taking in tens of millions of Amestrian souls he swells into a towering, single-eyed giant. Once he devours the power he calls God, he takes on a youthful Hohenheim-like body carrying, as he puts it, a miniature sun in his palm, able to bend nearly any natural law to his will.

While still the Dwarf in the Flask, the being was far warmer and more charming than the figure he would later become, polite and quick with a joke, brimming with what Hohenheim once called genuine human feeling, though even then a thread of superiority toward mankind showed through. As Father he turns intensely intelligent, manipulative, callous, and self-absorbed, hiding it all behind the mask of a composed, almost lifeless old man who barely bothers to feign interest. He credits this emptiness to having purged the seven vices from himself, yet the purge is never complete, and he keeps acting out the very sins he claims to have shed. When his plans near their end, the calm cracks into something manic and openly cruel.

His feelings toward humanity are tangled and self-contradicting. Outwardly he dismisses people as weak, foolish pawns beneath his notice, akin to insects, useful only as tools for his designs. Yet Hohenheim suggests he built the homunculi precisely because he longed for a family of his own, something Father does not deny, and he does have them call him their father. Above all he is fixated on knowledge and perfection, treating Truth as his own private god he intends to devour so as to become perfect, blind to how little he actually grasps the forces he hopes to command.

The entity that will call itself Father begins as a fragment of whatever dwells past the Gate. A Xerxesian alchemist serving the kingdom's ruler manages to trap that fragment in a flask, using the blood of a young slave marked only as Number 23. The captured creature, dubbed the Dwarf in the Flask, holds staggering knowledge, including the very foundations of what will become Amestrian alchemy. Unable to cast alchemy on his own, he befriends the slave, gives him the name Van Hohenheim, and teaches him toward his freedom. Over time, though, he grows envious of the human bonds he cannot share, and that wounded pride festers into a hunger to overtake even God.

When the vain King of Xerxes demands the secret of eternal life, the Homunculus has him inscribe a nationwide transmutation circle, then sacrifices every soul in the land, sparing only himself and Hohenheim, to forge what is probably the earliest Philosopher's Stone ever made. He fashions immortal bodies for the two of them, and a horrified Hohenheim breaks away. Moving on, the creature finds a new people, teaches them alchemy and comes to be called the Philosopher of the East, and hides himself beneath what becomes Central Command, acting as a barrier against the earth's energy so that alchemists unknowingly draw on the Xerxesian souls sealed inside him. From those souls he spawns his seven sin-named homunculi and takes the name Father, ruling the military state of Amestris as its hidden hand and shaping its wars into one enormous transmutation circle.

On the Promised Day, Father drains the souls of every Amestrian citizen, tears the Gate open with nothing but his hands, and swallows the power he names God, emerging youthful and, by his own claim, all-knowing. Hohenheim's counter-plan uses the moon's shadow to force those souls back into their bodies, and without them Father cannot hold the God within. In the long final battle, Greed turns his body into brittle carbon, Edward punches a hole through his chest so the last Xerxesian souls escape, and the power he stole drags him back toward the Gate. Facing Truth at last, he is condemned for stealing might that was never his and for cutting away his own desires, then hauled into the abyss he came from.