Mutant Massacre

"Mutant Massacre" was a 1986 Marvel Comics crossover storyline. It primarily involved the superhero teams the X-Men and X-Factor. The solo hero Thor, the New Mutants, Power Pack, and Daredevil crossed over for an issue each in their own comic books. The crossover was a surprise success, yielding sales boosts to the mutant-based books and prompting Marvel Comics' long-running policy of holding such mutant crossovers annually. The story depicts a massacre of the Morlocks during an attack by the Marauders. The X-Men, X-Factor, and Power Pack attempt to intervene, with the X-Men having three of their members injured in the conflict.