History
Proteus took possession of Phoenix, forcing the Soviet Super-Soldiers and the X-Men to join forces to stop them. Not wanting Phoenix to be killed, Professor X offered to become Proteus' host instead. Proteus agreed and possessed Xavier. Proteus then battled Colossus. Proteus severed Colossus's left arm, but Colossus took advantage of Proteus' weakness to metal by impaling Proteus with his transformed metallic arm, killing Proteus and Xavier.[1]