MUTANT MASSACRE was a large (for its day) event crossover storyline in select Marvel titles in 1986. The storyline ran through UNCANNY X-MEN, X-FACTOR and THOR, with tie-in issues in POWER PACK and NEW MUTANTS. A mysterious group called the Marauders enter the tunnels under New York and begin wholesale killing the Morlocks, a group of mutants who choose to live underground due to disfigurement and/or anti-social tendencies. The X-Men teams attempt to fight back but suffer some crippling injuries themselves. While hundreds of Morlocks were killed in the storyline, only a handful were named and, of those, only one had some background characterization established. While there were several dramatic consequences of the massacre, the one having the most lasting impact was the injury to Angel's wings necessitating their subsequent amputation. Prompted by the surprise success of this precedent crossover event, Marvel has demonstrated efforts to publish a crossover event approximately annually since. MUTANT MASSACRE is one of the earliest examples of a crossover event that does not require a reader to read every issue. Whereas some crossover events have numbered chapters and a defined reading order, with MUTANT MASSACRE, a regular reader of a single title could follow the portion of the story in their specific title or read other titles and tie-in issues to get more of the story and views of the same events from different perspectives.