When the Psions first arrived in the Vegan System, they found only two worlds inhabited by complex life forms. One of those worlds was Emana Branx, and its race of aggressive behemoths, the Branx Warriors. Unknown to the Psions, each Branx possessed a soul partner. When a warrior died, this angel of mercy carried his essence to a place of rebirth in some new, young Branx infant.
Capturing an adult Branx, the Psions coldly attempted to crossbreed him with a female from the other life - nourishing planet Okaara. The woman, X'Hal, was unable to resist the Branx's superior strength, but the union remained fruitless until the Psions detected the presence of the Branx's soul partner, and managed to tear him away from his proper place. The angel of mercy fled shrieking into the void in the form of a nimbus of black light.
Nimbus, as he came to be called, spent uncounted cycles wandering the Vegan star system. No longer able to create new life, his powers brought only death. Using that ability sparingly, NImbus found solace in helping the Vegan system's growing civilisations in an ambassadorial role.
When Primus began forming the Omega Men, Nimbus became his advisor and used his abilities in the rebel cause. The Omegan's relied on his experience, and he became a friend to many of them. Nimbus was the group's liaison to X'Hal and Auron, who heeded him as they never would a mortal.
It was that responsibility which led Nimbus to confront X'Hal and her son inside Vega itself, when he was concerned about her growing madness. The three became embroiled in a struggle which threatened the very existence of the Vegan system, until Nimbus and X'Hal found themselves swept through a time warp created by the original Crisis on Infinite Earths.
Emerging in a binary starlight system light years from Vega, X'Hal gained the upper hand and used the change-energy of the crisis to somehow compress 6 different dimensional versions of a nearby planet, making them one, with Nimbus trapped between them - bonded to the north polar region. Any attempt to free himself will lead to the destruction of the planet's diverse life forms.