Uncanny X-Men #376 (X-Men learn the identities of the Twelve, Living Monolith restored), Cable #75 (Cable captured by Apocalypse), X-Men #96 (Professor X recruited Magneto, Horsemen captured more of the Twelve), Wolverine #145 (Wolverine is given back his adamantium skeleton by Apocalypse and becomes Death), Wolverine #146 (X-Men helped Wolverine break free of Apocalypse's control), Wolverine #147 (Wolverine & Archangel deal with both having been Apocalypse's Horsemen), Uncanny X-Men #377 (X-Men & Magneto vs Apocalypse's forces, Twelve assembled), Cable #76 (Cable & Cyclops encountered Madelyne Pryor), X-Men #97 (Cyclops seemingly sacrificed himself to stop Apocalypse)
Astonishing X-Men #1-3 (X-Men vs Apocalypse's newest Horseman Death, Wolverine seemingly killed by Death), New Eternals: Apocalypse Now #1 (Apocalypse sought to foment war between humans & Deviants), Uncanny X-Men #372 (Bishop & Deathbird located Living Monolith adrift in space), Uncanny X-Men #373-375 (Deathbird delivered Living Monolith to Apocalypse, X-Men discovered dead "Wolverine" was a Skrull imposter), X-Man #59-60 (Nate Grey captured by Pestilence), X-Men #92 (Deathbird betrayed Bishop, joined Apocalypse), X-Men #93-94 (Polaris stalked by Skrulls), X-Men #94 (Shadowcat uncovered clues to the Twelve in Destiny's Diaries), X-Men #95 (X-Men discovered that Death is Wolverine)
In an attempt to gain godhood, Apocalypse gathers twelve powerful mutants, called the Twelve. He planned to take their powers and transfer them to himself. His body was not powerful enough, so Apocalypse decided that Nate Grey, the X-Man, would make a suitable host. The fabled Twelve that were gathered included; Cyclops, Jean Grey, and Cable for the power of family, Storm, Iceman, and Sunfire for the power of the elements, Polaris and Magneto for the power of the magnetic poles, Xavier for the power of the mind, Mikhail Rasputin and Bishop for the power of time and space, and finally the Living Monolith to funnel all the power to Nate Grey's body.