K'rll is believed to be the last Deonist, a race originating on the planet of Deo and ruling a Confederation of Planets. Deo eventually became Templeworld, so named because it housed the "One Above All" a gigantic god-like being who fed off the psionic energy of their worship in exchange for sustaining Templeworls's fragile biosphere. When a powerful space armada attacked their system, all of the Confederation except Templeworld fell. Their god sacrificed itself repulsing the invaders; with its last energy, it erected an immense spacewall around Templeworld to protect against further invasions; the northern pole was protected by constant meteor showers and the southern pole by seething stellar maelstroms. The surviving Deonist, calling themselves the Soul Survivors, captured another vastly powerful being, using him to provide the energy to protect themselves and preserve their world, which became known as the Doomsday Star. After fatally exhausting this being, they captured a replacement, repeating this as needed for an uncertain time period. K'rll became keeper of the Soul Survivors' gods, ruling alongside N'gll and developing a massive defensive arsenal.

The Deonist eventually captured the Asgardian god Odin in mid-transit between worlds. His son Thor and The Warriors Three (Fandral, Hogun, Volstagg), journeyed to find him. The Doomsday Star's defenses, powered by the Odinforce, captured most of the group, whom Deonist hoped to use as additional power sources. The immense energy drain pushed Odin past his limits, and he seemingly died after. As their restraints lost power, Thor freed himself and his allies, who overcame the now-weakened defenses. Confronted by the powerful gods, K'rll entered the "spirit mold," which animated a psionic energy construct empowered by the last stored portions of Odin's life force. Thor and his allies overcame the construct and freed the revived Odin. Without a godly life force to sustain it the Doomsday Star became uninhabitable and the Soul Survivors were forced to evacuate.

K'rll later re-entered the spirit mold, reformed the construct and re calibrated its psionic circuitry to tap his brethern's life force, slaying them all in the process. Now dwelling within the construct as the Soul-Eater, K'rll traversed the galaxy looking for places of death to feed upon fresh souls. He was near the Kree Empire's center at the conclusion of the Kree/Shi'ar war when the Nega-Bomb exploded on Hala. The Soul-Eater absorbed untold trillions of souls, increasing in size and power exponentially. The cosmic protector Quasar (Wendell Vaughn) was sent by the death rite fanatics known as the Mourners to investigate the lack of "true death" of the Kree Nega-Bombs victims. Quasar and his allies, the Eternal speedster Makkari and the genetically engineered Kismet (Her), quickly found their abilities insignificant against the Soul-Eater's power. The Soul-Eater then targeted the still-gestating form of the cosmic entity Origin. Quasar entered the Soul-Eater, encountering the souls of the Nega-Bombb victims and convinced them to resist the Soul-Eater, causing an internal reaction which blasted the Soul-Eater's form to shreds.