Written by CHRIS CLAREMONT, BARRY WINDSOR-SMITH, LOUISE SIMONSON & WALTER SIMONSON. Penciled by JOHN ROMITA JR., RICK LEONARDI, JUNE BRIGMAN, BARRY WINDSOR-SMITH, BRET BLEVINS, ALAN DAVIS, ARTHUR ADAMS, TERRY SHOEMAKER, WALT SIMONSON, JACKSON GUICE & JOHN BOGDANOVE. Cover by JOHN ROMITA JR. "Mutant" means "change," and there was plenty of that when the Uncanny X-Men counted down to the Marvel Mutant Massacre beginning with the trial of Magneto! Rachel Summers became Phoenix and the Brotherhood became Freedom Force! Lady Deathstrike became a cyborg, Moonstar a Valkyrie, Colossus a killer, and Psylocke an X-Man! And Sabretooth first set his clawed foot into the X-Universe alongside his fellow Marauders! Guest-starring the original X-Factor, Power Pack and Thor! Gods, Morlocks, talking frogs and more! Collects UNCANNY X-MEN #199-213, NEW MUTANTS SPECIAL EDITION #1, X-MEN ANNUAL #9, X-FACTOR #9-11, NEW MUTANTS #46, THOR #373-374 and POWER PACK #27. 656 PGS./Marvel T+