A being born at the universe's inception, Aarkus, considered a lesser counterpart to the Phoenix Force, harnessed its power for justice. From individuals of god-like might to entire worlds deemed evil, Aarkus wielded the Phoenix's Shadow to dispense justice.

Legion unintentionally released a fractured personality into the world, Aarkus decided to unleash it. Concerned that the rogue personality might overpower the Shadow Phoenix and pose a threat to humanity, Aarkus sought to test it on David, assuming its ability to kill him would extend to the fiend.

Later, it is revealed that the Shadow Phoenix may not actually exist; as it was revealed Karasu was posing as the cosmic entity. But the creature's entire history had been memorized by Aarkus, so its actual existence is still a possibility.

Karasu used her psychic powers to delve into his mind, exposing his flaws and pushing him to merge his personalities into a unique entity called "Gestalt." Defeating the Shadow Phoenix, David demanded an explanation for the deception.