This is Remnok. He is a Dragonic Demon, he is the inner being of a young cleric by the name of Marthus. Marthus was used as a test subject to try and summon the great demon Diablo through him. But it failed....sort of, the end result was Marthus having moments where he spazzes and his body shifts into this tubby lard of Demon. Marthus's spirit and soul being stored away in the painful confinds of the Ruby on his belly.