The Daedalus Enigma: Waves of Darkness Book 6 - Waves of Darkness: the Sisters of Power, #6

The sixth Sister of Power presents pirate-turned-vampire Viktor Brandewyne with his greatest challenge yet. Circe proves not only hard to reach: the quest she sets him is fraught with peril from the very start. he must brave a labyrinth to retrieve a puzzle box. He then must revisit each of the Sisters he's already faced. Five pieces of the box were dispersed among them by order of the Elder long before Viktor was even born. The completion of his quest is further barred by a sea dragon, the ultimate form of a male sire, who seeks to claim Belladonna as his mate. Before all is done, Viktor will lose someone very close and important to him. He also has to survive Circe's power; for she is the same witch from The Odyssey, with  the power to turn men to beasts.