The Bargainer (The Bargainer, #1-3)

This is the complete Bargainer series, and it includes the books Rhapsodic, A Strange Hymn, The Emperor of Evening Stars, and Dark Harmony within it.

Callypso Lillis is a siren with a very big problem, one that stretches up her arm and far into her past. For the last seven years she's been collecting a bracelet of black beads up her wrist, magical IOUs for favors she's received. Only death or repayment will fulfill the obligations. Only then will the beads disappear.

Everyone knows that if you need a favor, you go to the Bargainer to make it happen. He's a man who can get you anything you want ... at a price. And everyone knows that sooner or later he always collects. So when Callie finds the fae king of the night in her room, a grin on his lips and a twinkle in his eye, she knows he's finally here to collect. At first, all he asks for is a chaste kiss-a single bead's worth-and a promise for more. But Callie has a wrist full of debt, and the Bargainer has many, many demands.