Tales from the Viscount Volume I. Tales of Ardor, #4

Elven warrior Warren Dietrich has served his homeland well. For centuries, his family line has safeguarded the continent from every sort of threat, from bloodthirsty monsters to would-be conquerors. In this newfound era of peace, the warrior just might be able to settle into the quiet life on the coast he's always wanted. This all changes, however, when an old friend comes calling. The Guild of Sciences has a mysterious proposal to offer: Warren is to lead an expedition into the uncharted territories of their world.
Priceless discoveries await, but they'll come at a price. Few elves have ever ventured into those forbidden lands, and those who have never returned. Even with the evident danger and dark secrets of the looming expedition, the warrior elf is beckoned forth by a force he's never truly really been able to master. Enter a world of dark fantasies and sinful desires.