Curse of the Wolf (Magnetic Magic) by Lindsay Buroker

Luna has freed the charming treasure-hunting werewolf, Duncan, from the magical control device that let their enemies manipulate him. Finally, she can trust him fully, and they can explore a romantic relationship. Or so she thinks. But destroying that device had ramifications… A curse threatens to take Duncan’s life. If they can’t figure out a way to remove it, Luna will lose the man she’s come to care deeply about—maybe even love.