Ayden. Deamhan Minion - Deamhan Chronicles, #2.5

For over a hundred years Ayden, a Metusba Deamhan has waited for the chance to avenge his sire who met a bloody end at the hands of Anastasia, a Ramanga Deamhan. Being an obedient servant to Kyra, the oldest of their kind, he finally gets his chance to have his revenge. However, there's one small problem. He's heavily indebted to Anastasia's offspring, Maris and Kyra wants him to kill her. He must decide.
Be the obedient Deamhan minion to Kyra, who used the darkness inside him to fuel his rage or protect Maris, who saved him from that same darkness for a second chance to feel again. The choice isn't going to be easy. Then again, when has anything in his long tortured life been easy?