Hohenheim is the master of Hohenheim Lab, having been sealed there by Gryas. He first appears to Mattel urging him to leave his lab, and attacks when he does not listen. After the battle, he reveals that it was an illusion he conjured.
Later, Mattel encounters him again, this time in the flesh, to prevent him from continuing any further. He urges Mattel to reconsider his path, calling his cause trivial. After being defeated, he will reveal that he was first defeated by Paragon, then by Gryas, and that both of them stole the secret to creating Beasts and have used its power to their own selfish ends. He reincarnated in order to prevent any others from gaining this power, but finds that he is no longer able to reincarnate. He dies, taunting Mattel by telling him that he will not be able to escape his lab.
Trivia
Hohenheim is based upon Theophrastus von Hohenheim, also known by the name Paracelsus. Paracelsus is a notable figure in the alchemical canon and is considered the father of modern toxicology.
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