Ayden. Deamhan Minion. Deamhan Chronicles, #2.5

A centuries-old supernatural being must choose between the revenge he's waited a lifetime for and the person who helped save him from himself. For more than a century, Ayden has lived with a single purpose: revenge. A Metusba Deamhan bound by loyalty and haunted by loss, he has spent decades serving Kyra, one of the oldest and most powerful of his kind. In return, she offers him the opportunity he has long desired-the chance to settle a blood debt with Anastasia, the Ramanga Deamhan responsible for his sire's death.
There is only one problem. To carry out Kyra's wishes, Ayden must destroy Maris, Anastasia's offspring. But Maris is also the one person who helped pull him back from the darkness consuming him, offering him something he thought he had lost forever: a reason to feel. Torn between loyalty and redemption, vengeance and gratitude, Ayden must decide which path to follow. As old wounds are reopened and dangerous choices draw near, he learns that some debts are paid in blood-and others in sacrifice.
Set in the world of the Deamhan Chronicles, Ayden: Deamhan Minion is a dark urban fantasy novella about revenge, loyalty, and the struggle to overcome the darkness within.