Hall of skulls
(Book)

"When the provisional leader of the Mokuteki people is subjected to the brutal challenge of a lifetime, Kai soon realizes much more than just his title is at stake. To prove himself worthy of a leadership role he does not want, a torturous testing phase begins, one designed to break both body and spirit. As part of this challenge, while blindfolded and chained, Kai learns his betrothed, Asher, has been abducted. In his search for Asher and truth, trading deeds for information, Kai has not only to face the Thrakens--the alien invaders who had nearly conquered his world two-thousand years before--but also must fight against both time and space. Believing his future and that of Asher are inexorably entwined, he discovers his only hope is to unlock the ancient technology and secrets that lie within The Hall of Skulls."--,(source of summary not specified)