Father is the primary antagonist of the manga, Fullmetal Alchemist, and its anime adaptation, Fullmetal Alchemist: Brotherhood. Arguably the most powerful alchemist to have ever lived, Father is a major player in the Non Disney Villains Tournament, though he does very little fighting himself, instead choosing to act through his "children," the Seven Homunculi.
Non Disney Villains Tournament
Father originally hailed from Nothingness, a reality some religions have come to call/refer to as "Mu". Located inside the Gate of Truth, he was kept in there since the dawn of time, never really having a glimpse of anything other than what the void had to give him. He absorbed all the knowledge he could, and yet, he could never really take advantage of it. His entire being, his entire existence was merely condemned to a life in eternal darkness. Or so he thought.
Sometime, many centuries ago, the Gate of Truth was opened by the works of a strange woman, who seemed incredibly keen on learning the secrets of the world that surrounded her. Her name was Dante. No one knows how she opened the Gate without paying such a high price, but the small instances in which she did it were more than enough for Homunculus (who would later rename himself to "Father" ) to escape his captivity.
Sadly for the creature, though, it only existed as a small black orb inside a flask, unable to survive out in the open. Dante was a young enthusiastic woman though, and thus, she chose to study and aid this new creature who, so pleasantly provided her with all the knowledge of the occult she could come to need. In spite of her prominency in alchemy (which Father took the time to teach her), Dante alone had not enough power to complete the seal she and her new friend dreamed of.
The needed help came in the middle of the XVII century, when a young man known only as Vladislaus Draculia presented himself to Dante and Father, interested in opening the door to the occult. With his founded research and their keen intellects, they achieved their goals, creating a perfect circle of transmutation and sacrificing the lives of an entire country (sucking out their souls) to finally give Father his physical form...and immortality to Dante, at a price, however.
Assuming a form that reminded many men and woman of the portrait they painted of their Christian God, the Homunculus adopted the name of "Father", as it fit his new form and his growing desires in attaining perfection. Such came to happen when he removed all his seven sins from his personality, in order to become "perfect". Thus, the Seven Deadly Sins, a.ka Homunculi, were born.
Father gives out orders to his children, hoping to gain access to the world above. He has them work to gain entry into Ba Sing Se, keeping close tabs on a primary player in the war, Charles zi Britannia. Britannia is a blood relative of the man who created Father, a link to the "Great Evil." When one of his creations, Greed, goes AWOL, Father has it retrieved and sacrificed.
Encounter with the "Key"
As soon as Britannia rises up in power, Father makes his next move, by approaching the monarch, hoping to gain more informartion about him.