Darkest Desire by Evangeline Anderson

As a half Scourge/half Kindred warrior, Sirex has a savage side that he fears cannot be contained. Does his desire to dominate make him a Broken One—a male who takes pleasure in hurting women? He doesn’t know and refuses to find out. For years he has avoided falling in love…until Phoebe enters his life.

Phoebe Jenkins has a secret dream—she wants to submit to a loving but stern Dom. However, she’s never met a man who’s worth submitting to…until now. When she and Sirex are sent to the Twisted System—a trio of planets where extreme sexual practices are the norm—she must play his submissive so that they can fit in with the male-dominated society. But the situation quickly spins out of control when pretense turns to reality.
Can Phoebe and Sirex keep from blowing their cover and complete their mission without falling in love? And will Sirex embrace his Scourge half…or reject it and his one chance at love forever?
You’ll have to read Darkest Desire, the second book in the Twisted System series to find out.