Collects Uncanny X-Men (1981) #333-337; X-Men (1991) #53-57; Onslaught (1996): X-Men, Marvel Universe, Epilogue; Avengers (1963) #401; Fantastic Four (1961) #415; Wolverine (1988) #104; Cable (1993) #35. The biggest and best adventures of Marvel''s mighty mutants — these are the X-Men Milestones! And this event rocked not only the X-titles, but the entire Marvel Universe! For months, the force of nature known only as Onslaught has struck from the shadows — but when the X-Men discover Onslaught''s startling true identity, the villain''s plan kicks into high gear! Determined to punish mankind for a litany of sins, Onslaught laid siege to the X-Men, Avengers, Fantastic Four and more — kicking off a cataclysmic conflict destined to deprive a world of its most revered icons! Earth''s greatest heroes face their ultimate enemy in an explosive saga that transformed the Marvel Universe!