The Taming of Dracul Morsus - World of Dracul Morsus, #1

Abandoned as a child for his inborn gifts, raised by a dragon, Mage Dracul Morsus came to be the most powerful mortal man in the world. He has also renounced the world of men that reviled him for his power and his unwillingness to use it at their bidding. In his inaccessible mountain fortress, he has always had everything he needs. Or so he thought. When a god gone rogue and his divinely-empowered legion of zealots threaten not only the world of men, but the realm of the gods, Dracul Morsus has no intention of getting involved.
When Xana shows up on his doorstep, she has every intention of changing his mind. And being the last and best thing Dracul Morsus needs. Xana is a woman who will drive him to hell and back again. Literally. More than once. Because the most powerful thing in every realm is Xana's force of will.