One Silent Night by Sherrilyn Kenyon
Ruler of the Daimons, Stryker, unleashes an ultimate evil in hopes of finally killing off two of his enemies: Acheron and Nick. Unfortunately, his plan backfires.
Artemis sends one of her servants to kill Stryker. Much to his surprise, the assassin is his ex-wife, Zephyra. Even more to his surprise, they have a daughter.
Stryker convinces Zephyra to give him two weeks to prove that he still loves her. If he doesn’t prove it, he will willingly let her kill him.
Meanwhile, the duo must deal with a nasty demon problem – mostly caused by that the evil god that Stryker let loose. Can Stryker work with his enemies to save few of the only beings he has ever truly loved?