Applegate Katherine Alice. The Ellimist Chronicles

The Ellimist Chronicles is a children's science-fiction novel, a companion book to the Animorphs series written by K. A. Applegate. It tells the backstory of the Ellimist, a god-like being from the story. The introduction shows that the Ellimist is telling his story to an unnamed Animorph, foreshadowing the events of the final book of the series, and fulfilling the promise that one Animorph would die after being visited by the Ellimist.As an unnamed Animorph lies on the brink of death, the Ellimist appears and recounts to him/her his origins as Azure Level, Seven Spar, Extension Two, Down-Messenger, Forty-One (Toomin) the Ketran and his transfiguration into the Ellimist as a final request to the dying Animorph. The Ketran race was virtually extinguished by the Capasins, who had seen transmissions of violent virtual Ketran games that had been broadcast into space and mistook them for a violent species that meddled with other ones. Toomin/Ellimist was one of the few survivors. These survivors became space nomads, seeking a replacement for their home Ket. Toomin became the leader of this group and was the only survivor when it crash-landed on a mostly aquatic moon. His mind was absorbed and kept alive at the bottom of the sea by a moon spanning entity known as Father that absorbed the information in the brain (or equivalent) of every corpse on it. After defeating Father at music, Toomin began to grow too intelligent for Father and defeated him, incorporating all the memories of corpses on the moon, eventually becoming a blending of minds.