X-Factor

During a mission to the island nation of Genosha, one of Madrox's duplicates contracted the deadly Legacy Virus. When reabsorbed, it was believed Madrox himself was infected. The mutant prophetess Haven offered to cure Madrox of the Virus, but the attempt failed, and he seemingly died.

While in the South Seas island nation of Madripoor, the team became trapped in a confrontation between Lila Cheney and the alien race, the K'Lanti. Lila had stolen an object of great value, called the Harmonium, in the midst of political chaos. The aliens, after destroying a city block, disperse diamond-shaped bombs throughout the city. Despite the neutralization of the bombs and the return of their object, the aliens left behind one last explosive. Strong Guy absorbed the energy of the explosion. Despite releasing it with powerful punches, he suffered a powerful heart attack. He was forced to go into suspended animation.

Wolfsbane left the team, choosing to move back to her home, Muir Island, after learning her adopted mother, Moira MacTaggert, had contracted the Legacy Virus. She joined Excalibur.

Havok was captured by the Dark Beast. After Havok's disappearance, Forge assumed leadership of the team. The additions of Mystique and Sabretooth to the team, as well as their investigation into the Hound Program, caused them to question their role. Sabretooth escaped and attacked the team. They soon moved underground.