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...

"Following the events of Messiah CompleX, the X-Men are heading west, founding a new home for themselves, and all mutants, in a place known for its tolerance: San Francisco, California. Shortly after their arrival, however, the X-Men find themselves tangling with Magneto and fighting down the robotic, mutant-killing Sentinels. And as if that wasn't enough, Pixie, one of the youngest members of the team, learns just how dangerous bigotry is when she's...

"The Marvel Universe's two most powerful teams battle over the fate of the X-Man Hope. With the cosmically destructive Phoenix Force drawing ever closer to Earth, the planet's heroes have chosen sides, with the Avengers seeking to take the mutant Hope into custody, and the X-Men pledging to protect their mutant messiah at all costs. As the very future of mutantkind-- and possibly Earth itself-- hangs in the balance, the battle between X-Man and Avenger...