The Darkest Angel (Lords of the Underworld #4.5)

Winged warrior Lysander has been alive for centuries, and yet he's never known desire-until he meets Bianka. Spawned from the bloodline of his enemy, the beautiful but deadly Harpy is determined to lead the untouched Lysander into temptation. He may try to evade her attempts, but even the most iron-willed demon assassin can resist for only so long....