Marvel's greatest heroes sacrificed themselves to save the world from the deadliest threat they had ever faced: Onslaught! The lives of the Fantastic Four and the Avengers were saved only when Franklin Richards created a parallel universe, where we found those heroes, reborn! But this world has long since merged back into our own, and the evil Onslaught - forged from the most vile parts of Magneto's and Professor X's psyches - has been presumed long...