Magneto. Emma Frost. Mystique. Juggernaut. Mojo. Apocalyspe. The X-Men have gone head to head with a lot of foes over the years-some truly evil, some just crossing that vital line that moves them from ally to enemy. From the cold vacuum of space to the jungles of the Savage Land, from dominating the inner sanctum of a secret society to crashing through all walls in their way, these tales show what makes the X-Men's opponents the most formidable in the universe.