One of the most iconic and notorious X-Men crossover events of all time, this. Beneath New York live homeless street mutants, banded together for protection and pride, calling themselves the Morlocks after H.G. Wells monsters in The Time Machine, the evolutionary culmination of humankind after the fall of civilisation. Sent to exterminate the Morlocks, Mister Sinisters Marauders - mutant assassins and murderers, all banded together in one unholy outfit of killers - roam the tunnels and nothing can stop them, until the X-Men get word and descend below the city to defend their mutant brothers and sisters. The Mutant Massacre is one of the more scary and violent of the X-Mens past storylines, because X-Men are badly hurt and maimed during the course of the stories, and for the first time. Colossus ends up murdering one of the Marauders in a fit of rage after witnessing him butchering cowering mutants, and has to deal with the killing, unable to transform back to human out of his giant metal form: Nightcrawler is comatose and horribly wounded; Angel is pinned to the wall by his wings and used for target practice. Its also the making of Storm, as - accidentally rendered powerless by a weapon designed to protect humans from mutant villains - she rises to the challenge, becoming the leader of the X-Men despite lacking the ability to control the weather, and challenging the Morlocks leader Callisto to a knife fight for leadership of her band of street mutants.