The seismic ending of one era - and the beginning of another! 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 the combined strength of X-Factor and the X-Men to triumph - and when the dust clears, the two teams will become one! An uncanny new status quo is introduced as the reunited X-Men go back to basics, beginning with a deadly confrontation with Magneto and his fanatical Acolytes! 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 and X-FACTOR ANNUAL #6. Rated T