X-Men: Mutant Massacre Part One

In the abandoned subways and sewer tunnels of New York dwell the Morlocks — a group of mutant outcasts who hide from the world above. But what was once their sanctuary is soon to become a killing ground courtesy of a vicious cadre of assassins known as the Marauders. Standing between the Morlocks and almost certain annihilation are the X-Men, X-Factor and the New Mutants. A battle is coming that no mutant can walk away from, and one that will take a terrible toll on all involved...