Background and Basic Info
Father is the creator of the Homunculi. Starting out as a mere entity in a flask born from the Eye and the blood of a slave, the Dwarf in the Flask "Homunculus" gave the slave the name "Van Hohenheim", as well as knowledge to read and write. Helping Hohenheim to become an alchemist, the Dwarf in the Flash was asked by the King of Xerxes to aid in him attaining immortality. Little did the King know that the Dwarf, longing to be free of the flask and survive on its own, had ulterior motives.
The Dwarf gave the King plans for a country-wide transmutation circle. After quite the length of time, the circle was completed and then activated. Rather then grant the King his desired immortality, however, the circle claimed the souls of everyone in Xeres with the exception of Hohenheim. The souls were concentrated into making Hohenheim and the Dwarf into living philosopher's stones. In a single night, all the lives of the citizens of Xerxes had been claimed. When the Dwarf revealed himself, he was in possession of the King's body with the face of Van Hohenheim.
Over the next few centuries, Father created the nation of Amestris, spreading knowledge of Alchemy in the East and seemingly purging himself of sinful souls, which he would shape into his children, the Homunculi. It was revealed that his ultimate goal was to create a nationwide transmutation circle to claim the souls of the millions residing in Amestris. Using their energy along with five "sacrifices", he would open the Earth's Gate of Truth and absorb God, rendering himself a perfect being.
However, his plan was destabilized by Van Hohenheim, whom used souls from his own philosopher's stone to reverse the nationwide transmutation circle and restore everyone's souls. Unable to contain God for much longer without all the souls he'd accumulated, he was eventually defeated in a great final battle and taken by God back into the Gate and the abyss within.