Nimbus belonged to a race of beings who were spiritually bound to members of the Branx species of Emana Branx. When a Branx died, it was the function of these beings to ferry the Branx spirit to a newborn lifeform so that the cycle of rebirth could begin anew. Centuries ago, Psion scientists captured a Branx Warrior and attempted to crossbreed it with a native of the planet Okaara known as X'Hal. The experiment permanently severed the spiritual cord between the Branx and his 'angel' and the wraith transformed into an insubstantial nimbus of energy.
In the years that followed, Nimbus became a diplomat and liaison to the fugitives of the Citadel Empire (who controlled most worlds within the Vega star system). The strongest of the fugitives became known as the Omega Men.
