Magneto was presumed dead after the fall of Asteroid-M (X-Men, #3, 1991) but the seeds for Fatal Attraction were sown then. Magneto was betrayed by Fabian Cortez, An Acolyte, who while acting as a Magneto loyalist was manipulating Magneto's own powers by amplifying them to effect the illusion of recovery of wounds which Magneto had suffered from Wolverine's attack (X-Men, #1, 1991) .
Asteroid-M was destroyed as a result of Plasma blasts, done jointly by the Soviet and US Governments. The X-men escaped before the destruction but Magneto and his Acolytes (with the exception of Cortez, who escaped before Plasma Cannons were activated) chose to stay and be martyrs for their cause.
After gathering many Mutants to join Magneto's cause, Fabian Cortez ordered a massacre of Hospital staff and patients in Wauntaugh, Virginia to gain attention of the X-Factor (Havok, Polaris, Quicksilver, Wolfsbane, Multiple-Man, Strong Guy & Random) so that Cortez could lend legitimacy to his cause by having Magneto's son join the movement. The Acolytes attacked X-Factor at Camp Hayden and during that battle, Cortez tried his best to lure Quicksilver into his movement i.e. genetic cleansing of "Flat-scans" in the name of Magneto but failed in doing so.
Yes, the warrior was Cable who was also presumed dead in the X-Tinction Agenda event where both him and his clone, Stryfe, were sucked into a time-stream. Cable had luckily escaped the stream and returned to Earth where he lived into hiding with his compatriots namely Domino, Grizzly and G. W. Bridge. Cable decided to reunite with his X-Force team by paying them an un-announced visit at their then HQ: Camp Verde, Arizona. While the team was finding it hard to believe that Cable was really alive, another un-invited guest suddenly emerged. This other guest was Magneto's apostle who came to Earth to invite the children of atom for a meeting with his Overlord (i.e. Magneto). Sam (a.k.a Cannon-ball) agreed to it and took with him Boom-Boom, Rictor, Sunspot, Rusty & Skids. Before leaving for his meeting with Exodus' Overlord; Sam had secretly placed a Comm-Link tracer on Cable's shoulder so that he can follow him, in case there was trouble. Cable, along with Warpath, Shatter-star, Feral & Siryn followed Sam's trace into outer-space and came to realize that the place where Exodus had taken some of his team members was actually Cable's former base a. k. a Graymalkin. Bitter, Cable decided to teach the man responsible a lesson by rescuing his X-Force members and blowing the whole place up. While doing so, Cable came across two old acquintances. First was his old sentient programme called "Professor" and the other was Magneto. Now knowing that it was Magneto who snatched Cable's base and the equipment along with it and dared to seduce his young team members into joining his fanatical Messianic movement for Mutantkind, he entered into his most dangerous fight of all time with the Overlord Magneto, where he almost ended up by paying with his life but he had succeeded in convincing and teleporting X-Force back to the space-craft. This was the first defeat for the Lord of Fatal Attractions (Magneto) and more was on the way for him and his acolytes.
The story starts with the conviction of Fabian Cortez by Exodus and the Acolytes regarding his role in the murder of their savior, Lord Magneto (X-Men, #3, 1991) and dethronment from his post as the Leader of Magneto's cause. Magneto is doing his preparations for his Ultimate showdown with his old friend Charles Francis Xavier, by appearing un-announced in Illyana Rasputin's funeral being held at the X-Mansion where all the X-Teams are gathering for the painful event of her burial. Using Illyana's death to prove his point, Magneto intends to recruit as many mutants as possible to take them away from a Planet where they are most hated, to a sanctuary called Avalon. Colossus, Illyana's brother, mired with depression and loss of hope, tells Xavier that his dream and his cause had failed both him and his sister, it was actually Xavier's dream of human-mutant harmony that resulted in Illyana's death. At that moment in time, Magneto appears and takes delight in humiliating his friend for failure, announces that those Mutants who do not join him to his Sanctuary will be considered as enemies to Lord Magneto's cause. Before he could leave, Magneto gets attacked by Bishop and thereafter by every X-Team mutant except for Colossus who attacks Bishop from behind and saves Magneto. Such an act of betrayal hit the X-Men in general and Professor X in particular, too hard. Watching Peter Rasputin being uplifted to Avalon was the worst thing X-Men had scene since Jean Grey's death as Dark Pheonix. Xavier didn't give-up, it was time for round two.
Xavier is bitter, The Magneto Protocols have been implemented & Magneto is provoked by it. He goes out of his safe-haven and cuts the Electro-Magnetic field which results in a Colossal power failure on Earth. To avoid a bigger confrontation, Xavier moves in with his team (himself, Wolverine, Gambit, Jean Grey, Quicksilver & Rogue) to Magneto's safe-haven (Avalon) to put an end to this cycle of violence...once and for all. For Xavier and his strike force, its a suicide mission and thanks to an old ally (Colossus) they are able to breach Avalon's security. The Strike team successfully teleports the whole of Avalon farther away from Earth and with it, an angry Magneto enters. The battle begins, a no-holds barred event and its biggest casualty turns out to be Wolverine who while striking a bold attack on Magneto has his famous Adamantium skeleton extracted by his Magnetic counter-attack. This infuriates Xavier, and he finally does something which he deemed unethical throughout his life, he takes away Magneto's mind via a strong telepathic attack. Both sides are bruised badly and the X-Men escape from Avalon by bieng rescued by Bishop who was duly informed by Colossus as the teleportation had disbanded the fortress' teleportation system. And in the post-war silence, as the writer stated, "One can hear the fading of a dream".