Soul of a Witch by Harley Laroux

Everly
I am the servant of a merciless God. I am the daughter of Its preacher. All my life, my power has been controlled by others. They raised me to be meek and stifled my magic.
But no more.
A brutal murder led me to discover a mysterious house full of magic – and the ancient, powerful demon within. He says my power can change the world, that I can kill the evil creature I once worshipped.
But at what cost?

Callum
For two thousand years, I’ve been alone. Slaughtering fallen Gods as I searched for the witch that haunted my dreams, begging for my help.
Now that I’ve found her, I will protect her with my life. But when the fate of Earth, Heaven, and Hell hangs in the balance, not even her soul is safe from destruction.
If a choice must be made, I’ll let the world burn if it means having her as my own.