X-Men #100 (1991 First Series)

"End of Days"

Six months have passed since the great sacrifice that saved the world from the evil of Apocalypse. In the intervening days, the characters we've grown to love have undergone startling changes. Professor X has left?  but where has he gone?! Nightcrawler has returned to an aspect of his past, but to what?! Shadowcat has turned to a darker side of herself, but why?! Rogue may have found something long missing in her life, but what is it?! And, in the shadows, from above and below, the X-Men have been targeted by a new enemy, one that may be even more powerful and ruthless than En Sabah Nur himself! Who, or what, are the Neo?!