Man of Two Worlds

On the distant planet Dreenor lives the most powerful species in the Galaxy. All of the Universe is the creation of the Dreens, who possess the power of "imaging", turning their thoughts into reality. They can create whole worlds, of which the wild, ungovernable planet Earth is one. But suddenly Earth is a threat, its people on the verge of discovering interstellar travel, and with it, of gaining access to Dreenor itself - a paradox within a paradox, not to be permitted.
While the elder Dreens plan Earth's destruction, a youngster, Ryll, embarks on an unauthorized jaunt across space. Forced for survival to merge bodies with an “Earther” whose mind is as strong as his own, he has to battle for control.
And the future of all earthly life lies in the hand of a composite being, half wily, aggressive human, half naive adolescent alien, confused and far from home.