Mutant Massacre

"Mutant Massacre" was a major Marvel Comics crossover storyline, which took place during late 1986. It primarily involved the superhero teams the X-Men and X-Factor and 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 huge sales boosts to the already popular mutant-based books, and ultimately prompting Marvel Comics's long-running policy of holding such mutant crossovers annually.