Falcons of Narabedla by Marion Zimmer Bradley

Falcons of Narabedla is a science fiction novel by Marion Zimmer Bradley set in the universe of her Darkover series.
Somewhere on the Time Ellipse Mike Kenscott became Adric;
and the only way to return to his own identity was to find
the Keep of the Dreamer, and loose the terrible
FALCONS of NARABEDLA