Onslaught was a sentient psionic entity created from the consciousness of two mutants: Professor Charles Xavier, the telepathic founder of the X-Men, and the mutant known as Magneto, Master of Magnetism. During a battle between the X-Men and Magneto’s Acolytes, Magneto extracted the Adamantium from the skeleton of Wolverine. Upon seeing this, a very angry Xavier used his telepathic powers to shut down Magneto’s mind, rendering him catatonic. During the psionic contact, Magneto’s anger, grief and lust for vengeance entered Xavier’s consciousness; that and with every long-suppressed negative feeling Xavier had endured during the last 30 years. This aggregation resulted in the being known as Onslaught, a being made of psionic energy combining Magneto’s and Xavier’s psyches.