Père, known in the original Japanese version as Father (Otō-sama) and earlier in his existence as the Homunculus or the Dwarf in the Flask, is the main antagonist of the Fullmetal Alchemist manga and its 2009 anime adaptation, Brotherhood. He is the first of the artificial humans, a being born from alchemy rather than nature, and he functions as a living Philosopher's Stone containing the souls of hundreds of thousands of people.

His background begins in the ancient kingdom of Xerxes, where court alchemists accidentally created him using a drop of blood from a nameless slave, later named Van Hohenheim, combined with the essence of the entity that dwells beyond the Gate of Truth. He came into existence as a small, dark, gaseous creature confined to a glass flask. Although he could not survive outside the flask, he possessed immense knowledge of alchemy and the workings of the world, knowledge that surpassed nearly every other being except the Truth itself. While imprisoned, he befriended the slave Hohenheim, gave him the name Van Hohenheim, taught him to read and practice alchemy, and helped him rise from servitude to an independent life. Later, when the king of Xerxes grew obsessed with immortality, Father used the king's ambition for his own ends. He instructed the king to cover the entire nation in a transmutation circle, and when the king activated it, the circle converted every citizen of Xerxes into a Philosopher's Stone. With that enormous power, Father was able to leave the flask, taking on a human body that closely resembled Hohenheim because it had been shaped from Hohenheim's blood. Hohenheim also received part of the stone, becoming immortal as well. Afterward, the two immortals separated; Hohenheim traveled east to Xing, while Father went west and eventually came to rule the nation of Amestris from behind the scenes.

In terms of personality, Father is cold, calculating, and deeply patient. He views human beings as insects or mere tools, and he discards anyone without hesitation once they no longer serve his plans, regardless of how loyal they have been. He behaves with a calm, measured superiority and shows little genuine emotional investment in the world around him. This detachment was not always complete. Early in his existence he was more charismatic and capable of forming bonds, as seen in his friendship with Hohenheim. However, he deliberately removed the seven aspects of himself associated with the seven deadly sins and shaped them into the homunculi, believing that purging these emotions made him closer to a perfect being. In doing so, he became colder and more hollow. Despite his claims to have transcended human weakness, his actions reveal envy toward human connection, emotional intimacy, and the limitations that give human life its meaning. He seeks to possess what humans have while simultaneously despising them for having it, and his inability to understand self-sacrifice and genuine bonds ultimately contributes to his defeat.

His motivations are built around freedom and the desire for absolute perfection. At first, he wanted merely to escape the flask and exist freely in the world. After achieving that, his ambition expanded into a plan to become godlike. He intended to open the Gate of Truth belonging to the planet itself, seize the being referred to as God or Truth, and contain it within his own body, thereby gaining complete knowledge and power. To make this possible, he spent centuries shaping Amestris into a vast transmutation circle. He incited wars and suffering, including the civil war in Ishval, to channel human souls and carve blood runes across the country. He also gathered five human sacrifices, individuals who had already passed through the Gate of Truth, because their presence was required to unlock the planetary gate. All of this was meant to culminate on the day of a solar eclipse, known as the Promised Day, when he would activate the nationwide circle, absorb the souls of all Amestrian citizens as fuel, and pull God down from the heavens into himself.

His role in the story is that of the primary antagonist and the hidden force behind nearly every major conflict in the series. As the creator and leader of the homunculi, he directs their actions from his underground chamber beneath Central Command, using figures like King Bradley, who is himself the homunculus Wrath, to control the military and the state. The homunculi act as his limbs, and he regards even them as expendable. On the Promised Day, he successfully absorbs the souls of Amestris and attains a godlike form, but his triumph does not last. Hohenheim had secretly prepared a counter-circle that used the shadow of the eclipse to return the citizens' souls to their bodies, depriving Father of his power source. Separately, the research of Scar's brother made it possible to destroy the underground walls that carried the nation's transmutation array, which allowed alchemists to fight him freely. Weakened and forced onto the surface, Father engages in a prolonged battle against the Elric brothers and their allies. Eventually, Edward Elric pierces his chest, releasing the being Father had tried to contain. The power drains out of him, and he is dragged back through the Gate of Truth, where he is reduced to his original form as the Dwarf in the Flask and pulled into the void beyond the gate, never to return.

Regarding his key relationships, the most significant is his connection to Van Hohenheim. Father was created from Hohenheim's blood, was named by no one, but instead chose Hohenheim's name, and the two shared the responsibility for Xerxes's destruction. Where Hohenheim came to regret the past and devoted himself to undoing Father's plans, Father saw their shared origin only as the foundation for his own ascension. He relates to the Elric brothers primarily as tools, specifically as two of the five human sacrifices he requires, though Edward ultimately becomes the one who defeats him. He also stands in a paternal relationship, in a twisted sense, to the homunculi, who call him Father and Father-in-law in different translations. They are extensions of his own discarded sins, and he treats them with cold practicality, even erasing Greed when that homunculus defies him a final time.

His development is unusual because he remains fixed in his goals for most of the story, showing no change of heart and no willingness to reconsider his path. What develops instead is the revelation of his origins, which exposes the emptiness beneath his calm exterior. His final moments, in which the Truth appears before him in a form identical to his own and delivers the judgment he had once described as proper despair for those who overstep their bounds, bring his arc to an ironic close, as he experiences the very fate he sought to avoid.

His notable abilities are extensive and drawn from the Philosopher's Stone within him. He is effectively immortal, capable of regenerating from wounds using the souls he carries, and he can reshape his body at will, having originally existed as a formless black gas and later learning to maintain his existence even without a defined vessel. He can perform alchemy without a transmutation circle and possesses centuries of accumulated knowledge. He is able to create other homunculi by separating parts of his own being, each embodying one of the seven deadly sins. After absorbing God during the Promised Day, his power increases dramatically, allowing him to fly, unleash destructive force, alter matter on a massive scale, and control his body's structure with precision. Maintaining this godlike state requires enormous amounts of soul energy, and he consumes the Philosopher's Stone's power rapidly in battle. When that energy runs out, his body deteriorates, and he becomes vulnerable to the same laws of alchemy he had sought to master. His defeat begins with the loss of his stored souls and ends with him being reclaimed by the Truth from which he originally came.