Alexander Nero spent most of his life in a mental asylum, being treated for several mental disorders such as schizophrenia, paranoid delusions, and bi-polar disorder. Nero claimed his parents were abusive, although given his state of mind, such assessments should not be taken at face value.
Nero was the second person recruited by the Qwardians to take down the new Green Lantern Kyle Rayner, the first being Fatality. In order to find someone with the same imagination and artistic skill as Rayner the Qwardians sought out Nero, who had a history of drawing violent and dark pictures in the asylum. Nero was designed as the "archenemy" of Kyle Rayner, seeing how both are artists with limitless imagination. He escaped from the asylum only to be confronted by a both the original Green Lantern Alan Scott and Kyle Rayner. A battle ensued and Alan Scott was seriously wounded, forcing Kyle to retreat and call upon the assistance of the JLA. Kyle Rayner asked the JLA not only to stop Nero but to be prepared to kill him, reasoning that Nero's ring was one of the most powerful weapons in the universe and his insanity made him a profound threat. While the JLA declined his request, they were unable to stop him in several hit-and-run skirmishes. In the end, the Flash found tapes of Nero's parents and Kyle played the images. Eventually, the images consumed Nero, terrorizing him and resulting in his defeat.
Nero returned a short time later when the residual Central Power Battery energy made itself known (it was left in the sun following the sacrificial reignition by Hal Jordan during The Final Night). Both Kyle and Nero's power levels were greatly increased and they waged war in space to see who would lay claim to the power. Kyle was eventually able to defeat Nero and claim the power (which caused him to become Ion for the first time) and it was believed that Nero was taken or rescued by the Qwardians.
Nero was seen when the villainous Ultra-Humanite imprisoned all super-powered beings of Earth and brainwashed them into becoming his private army.
One Year Later
Alex Nero returned, revealed to have masqueraded as Kyle during previous issues by Hal Jordan, who confronted him for his crimes. Nero is presumed responsible for the massacres once thought to have been committed by Kyle. After a battle with Kyle and Jordan, he is rendered into a vegetative state after being overwhelmed by Ion's power. Before he becomes totally vegetative, he reveals that he was forced to masquerade as Ion by an unknown group. Kyle proceeds to Oa to seek answers from the Guardians of the Universe, bringing Nero with him. However, when Nero awakes on Oa in the Guardians' presence, he seems to spontaneously release a massive amount of energy, as though exploding. Held captive by the Guardians of the Universe, still broken and unstable but now conscious again, Nero revealed that he couldn't name his mysterious contractors. The Guardians confirmed that the same foe or foes that set Alex Nero (and Effigy) against Kyle had altered Alex's mind, expunging all his knowledge about the mysterious group.
Nero was released from his prison along with Superboy-Prime and others during the Sinestro Corps' assault on Oa. Nero hid and eluded capture before finding and confronting Kyle and Sodam Yat near Oa. During the battle it was revealed that the Sinestro Corps had been responsible for manipulating Nero into impersonating Kyle. Working together, Kyle and Sodam Yat were able to defeat the mad artist and return him to his Sciencell. Despite possessing a yellow ring, Nero is not a member of the Sinestro Corps.
Nero was later executed in cold blood by the Alpha Lantern Corps as ordered by the Guardians of the Universe. During the Blackest Night, he was reanimated as a member of the Black Lantern Corps