Xum is the last survivor of a mighty race. For tens of thousands of years, ever since the catastrophe which destroyed his world, he has existed and waited. Keeping watch over his children, locked in their egg-like shells, unable to be born into a place where there is neither life nor hope. It was until a strange object approached from the void. Instinctively Xum recognized it as the product of civilization.

Using skills he had almost forgotten, Xum entered and thus set in motion a chain of events that could mean the end of Green Lantern. He passed close to the Justice League of America. Using his amazing powers he was able to see inside the sattelite. See Wonder Woman, the Batman and the Flash. Then, slowly he began to imitate what he has observed.

Xum found the perfect world where his two unborn children would ensure the continuance of his race. Unfortunately, that world was Earth , and the only way to make it a suitable environment was to destroy the ozone layer, which would extinguish all other life on the planet. Shifting from his natural gaseous state into humanoid form, Xum called himself Replikon, and for good reason: besides assuming a hybrid appearance that copied the elements of several members of the JLA, He was also able to duplicate those heroes’ abilities. Replikon also took on a human form and called himself Andre, then proceeded to learn everything he could about Earth from Carol Ferris, the one time love of Green lanterns; Hal Jordan.

Ultimately, Jordan, Green Arrow and Black Canary thwarted Replikon, then returned him to the asteroid belt form where he came. There, he later encountered Green lanterns John Stewart and Katma Tui, who understood the alien’s plight and built him a world within the asteroid belt. Replikon gave birth to Sachi and Yukinori, and the family of three lived happily ever after - that is, until the alien having undergone some alterations, recently returned to Earth, battled Superman in Metropolis, then inexplicably died moments after being defeated. Then Superman faced Xum’s son. Evidence suggests that the Replikons were controlled by an unseen hand, one with particular interest in the Last son of Krypton.

It was later revealed that the villain Ruin (revealed to be Emil Hamilton) was behind Xum’s return, as well as his son’s attack on the Man of Steel .