Collecting X-Men Annual (1970) #15, X-Factor (1986) #65-70, Uncanny X-Men (1981) #278-280, X-Men (1991) #1-3 and material from New Mutants Annual #7 & X-Factor Annual #6.
The end of an era for the X-Men! The original team, now called X-Factor, takes center stage when Proteus returns from the grave. But when Apocalypse strikes, infecting Cyclops' son Nathan with a deadly virus, Cyclops must make a bitter sacrifice! And the current X-Men return to Earth to find that Professor X's old foe the Shadow King has risen -and taken over Muir Island! It will take X-Factor and the X-Men's combined strength to triumph...and when the dust clears, the two teams will become one! An uncanny new era begins as the reunited X-Men go back to basics - beginning with a deadly confrontation with Magneto and his fanatical Acolytes!