Nightbred - Lynn Viehl

Jamys has survived being made an immortal Darkyn, horrific torture and years of gruelling warrior training. But he has nothing to offer Chris, the mortal woman he loves. When he learns of a lost treasure, he vows to possess it and win her heart. Yet he doesn't know Chris wants to be a tresora, a human servant of the Kyn, so she can live with Jamys. Her superiors offer to make her dream come true, but only if she finds the treasure first. They cannot be kept apart, and working together they track the jewels through shadowy mazes and against ruthless opponents.