Age of Apocalypse - Secret Wars #1

Plot

His war has been won. The few humans left alive are enslaved, the mutant rebellion crushed. EN SABAH NUR, the APOCALYPSE, rules his BATTLEWORLD kingdom without mercy, but the terrorist X-MEN plan to end his reign. Success means finding one very special mutant named CYPHER and unleashing a weapon that will kill Apocalypse -- and possibly all mutants, too!