After gathering the remaining Acolytes after Asteroid M was destroyed in X-Men, Magneto captures the space station Graymalkin from Cable (nearly killing him in the process) and renames it Avalon. Sending his Acolytes, especially the newest member Exodus, out to recruit “worthy” mutants to his sanctuary Magneto attempts to create a nation of mutant-kind. Magneto himself arrives at Illyana Rasputin’s funeral and Colossus agrees to join him.
Feeling threatened by his activities, the U.N. enables the “Magneto Protocols”, a network of satellites which would prevent him from using his powers (and therefore bring more mutants to Avalon) within Earth’s atmosphere. Magneto destroys the network with a massive electromagnetic pulse, blacking out the entire planet and killing thousands.
The X-Men retaliate with a small strike team, including Professor X in a Shi'ar exoskeleton, which slips into Avalon, attacking Magneto. In the course of battle, Magneto rips the adamantium from Wolverine’s skeleton. In retaliation Xavier wipes Magneto's mind, leaving him in a vegetative state.
Both sides withdraw, but a seed of Magneto’s rage remained hidden within Xavier’s psyche and they merged later to create to psychic entity Onslaught.