The solo hero Thor, the New Mutants, Power Pack, and Daredevil crossed over for an issue each in their own comic books.

The two teams however do not meet during the battle and suffer crippling losses: X-Factor's Angel is crucified by the Marauders,[4] while the X-Men's Colossus, Shadowcat, and Nightcrawler are all severely wounded.

[8] Several Morlocks, including Berzerker and Masque,[9] make their way into the surface world and begin to work for their personal aims.

Writer Chris Claremont originally conceived the systematic killing of the Morlocks as a storyline that would run in the pages of Uncanny X-Men, but X-Factor writer Louise Simonson felt that such a big storyline would run overlong in a single title, and suggested that it be done as a crossover between all three mutant titles.

[1][16] Claremont and Simonson, the chief writers of the crossover, exchanged copies of their typewritten plots and scripts, and extensively discussed the intersecting storylines over the telephone.

[16]In The Gifted episode "calaMity", The Purifiers murdering all of the Morlocks in their tunnels was the premise of the "Mutant Massacre" storyline.