Gazer was an astronaut permanently stationed alone on a NASA observation space station, due to the unusual metabolism he possessed as his mutant power, whereby he could absorb harmful radiation and process it to gain sustenance. He first encountered the X-Men when they used his station as a staging post for an attack on a group of non-sentient aliens which induced harmful emotions in humans.
Shortly afterwards, he lost his powers on M-Day, along with 90% of mutants. Succumbing to radiation sickness, he began to imagine that an experiment on the effects of radiation sickness was sentient (calling it "Phantom Torso"), and it constantly advised him to call NASA to ask for a return home. However, he remained until an alien resembling Doop, which he'd built up to himself as his last hope, passed by his station on its way to crash-landing on Earth near Polaris, who'd seen it in space and had a similar reaction.
Thereafter, "Phantom Torso" stopped "talking" to him, and he put on a spacesuit and went out into space to die. However, he was teleported to Apocalypse's sphinx-like ship, and forced to battle Dr. Foster, a human archeologist who had stumbled upon Apocalypse's tomb, for the "right" to become War, Horseman of Apocalypse. Gazer would have lost the battle if it were not for Ozymandias, Apocalypse's servant. Ozymandias told Gazer that he would owe him and one day the scribe would become the master.
Gazer went through a terribly painful process where his skeleton was stretched, the former X-Man Sunfire, who was also chosen by Apocalypse to be a Horseman, tried to save him but Gazer had already been under Apocalypse's mind-control by then and helped recapture Shiro. As War, Gazer was sent to battle the X-Men and Sentinel Squad O*N*E. Upon returning to Apocalypse's sphinx, he was approached by Ozymandias who wanted his debt repaid. War, no longer Gazer, did not fulfull his oath and instead revealed the truth to Apocalypse about Ozymandias' treachery.
During a heated battle against the X-Men, Ozymandias finally took his vengeance, stabbing Gazer from behind with a sword.
Before M-Day, Gazer, in addition to his unusual appearance, could absorb radiation at frequencies and levels which induce radiation sickness in normal humans and photosynthesize it as food.
After his depowerment on M-Day, he was taken by Apocalypse and transformed to possess super-strength and enhanced durability, and the ability to absorb and rechannel solar energy as blasts of fire through his eyes. He also carries a spiked mace which flashes with electricity-like bursts, and rides a robotic horse-like flying machine.