Warren Worthington III was a mutant who received his angelic wings at a young age along with a unique healing factor in his blood. Warren briefly became a costumed superhero known as the Avenging Angel. He caught the attention of Professor X, who recruited him as the third of five founding members of the X-Men. Warren would conceal his mutation with a harness that Xavier created. He was later a founding member of X-Factor.

Warren was brainwashed and began to serve Apocalypse. Apocalypse warped his body and mind into his own "Angel of Death" upon his Celestial Ship and placed him into his team of Horsemen as Death. Warren's skin turned blue, he grew a set of bio-metallic wings from his back that could retract and also fire dart-blades with a neurotoxin. Warren's new wings could fly higher, faster, and were razor sharp.

As Death, Warren fought the rest of X-Factor and captured them. After X-Factor's defeat, the Horsemen were sent into Manhattan to incite chaos. Warren was shocked back to his senses after Iceman faked his own death at Warren's hands by having him destroy an ice sculpture of Bobby. Continually fighting an inward battle against his killer instincts, Warren eventually learned to control his wings through concentration. He eventually regained his original, feathered wings, when his techno-organic ones "molted" away and his skin returned to its normal color.