Dream Warrior by Sherrilyn Kenyon
The son of Warcraft and Hate, Cratus has spent eternity battling for the ancient gods who birthed him. He is death. Now that an ancient enemy has been unleashed, Cratus's task is to destroy it.
Delphine Toussaint is a philanthropist whose passion is for world peace. When a chance meeting brings her together with Cratus, the two develop a striking bond. Cratus is at first baffled by this human and her open nature...but soon he realises that Delphine is the key to completing his mission.
Delphine, meanwhile, is troubled by nightmares that are starting to become a reality. The only comfort she can find is around Cratus. But she refuses to give in to war, and he refuses to lay down his arms. Yet one of them must give in, or humanity will pay the price...