Homunculi (Fullmetal Alchemist)

Homunculus is the main villain in the Fullmetal Alchemist: Brotherhood anime series.

Origin
Homunculus is a mysterious being created from the blood of Hohenheim Elric. For the beginning of his life, he was kept inside a flask, having no real solid form to assume. He appeared as a black, shadowy orb with one large eye and a very wide smile. Forming a friendship with Hohenheim, Homunculus granted the man knowledge of various academics, including math, science, and alchemy. King Xerxes, the leader of the region where Hohenheim lived, strongly desired immortality, and commanded Homunculus to explain how to achieve immortal life. Homunculus instructed him to form a transmutation circle around the country, with a large massacre at every point. King Xerxes followed the directions of Homunculus, and was, then, instructed to stand at the center of the transmutation circle, where he would receive his immortal body. However, Homunculus tricked Xerxes into standing away from the center, where Xerxes was killed. Homunculus, smiling, looked up at Hohenheim, who was holding his flask, and told him that he and Hohenheim were standing at the true center of the transmutation circle. Everyone in the region was killed, except for Hohenheim and Homuculus who both received immortal bodies formed by the souls of the people who had been sacrificed. Hohenheim, horrified by what Homunculus had done, left Homunculus, vowing to kill him one day.