Bishop came to the future to fend off the one mutant who betrayed and destroyed the X-Men. He thought it was the ever mysterious wise acre, Gambit. Little did he know that it was Charles Xavier himself. The professor has a very well trained and harnessed mental ability. Used only for good. However, this tigh control over his psyche has unleashed an evil twin on two occasions. Once was during a battle with Magneto when he completely erased Magneto's mind. When all was said and done, Xavier's dark side - his suppressed rage at the human bigotry - integrated with Magneto's very soul. This creation combined Xavier's hate and rage with Magneto's power, his ver essence. It is almost as if the two men had a child. This creation was called Onslaught.

Onslaught's body and amor are made entirely of psionic energy. Onslaught enveloped Xavier into his body, stripping him of his powers and weakening the X-Men. X-Man (an incarnation of younger Cable from another timeline) was also enveloped for his colossal power. He acts completely independently of his two creators. He used sentinels and took control of Manhatten. This eventually raised the bigotry against mutants to the Operation: Zero Tolerance timeline led by Bastion.

The X-Men turned their full powers against him. They were joined by various other teams such as the Avengers. When Franklin Richards, son of two members of the Fantastic Four, was kidnapped, Onslaught enveloped him into his own body and absorbed his powers to restructure reality. The Fantastic Four joined the fight and eventually they destroyed Onslaught from the inside out. But in the mutant reality, no one really "dies." Right, Jean?