He is the main antagonist of Fullmetal Alchemist. He was a homunculus created from the blood of Hohenheim. In this first form, he was a small black orb with a single eye, mouth, and little arms. He was called "Homunculus" by his creators, or "Dwarf in the flask" by Hohenheim due to being trapped in the flask that housed him.

Later, he took on Hohenheim's form and created the seven homunculus from his own body and had them call him "Father".