The Invisible Ring (The Black Jewels 4)

Jared is a Red-Jeweled Warlord bound as a pleasure slave by the Ring of Obedience. After suffering nine years of torment as a slave, he murdered his owner and escaped—only to be caught and sold into slavery once again.
 
Purchased by a notorious queen, Jared fears he will share the mysterious fate of her other slaves—never to be seen again—and so prepares himself for death. But the Gray Lady may not be what she seems and Jared soon faces a difficult decision: his freedom, or his honor...