Devouring Kiss by Karen Kincy

I am a monster with royal blood, and my mate breathes fire.
They whisper my name in fear—the Gray Prince, the bastard son of the king and his succubus courtesan. A prophecy claims I will sit on the ruined throne, but the last thing I need is the dead weight of a crown on my head.
Nothing matters to me but Pyrah.
My dragon shifter mate brings light to the otherwise dark gloom of my life. I would do anything to protect her. But another dragon stalks Pyrah, hungering to make her his own. Worse still, the queen’s knights hunt us relentlessly—not to kill, but to capture. Whatever sinister plot the queen weaves, Pyrah is the missing thread.
I have lived in the shadows, an outlaw prince dreaded by the kingdom. But for Pyrah, I will become the monster they always feared I was.
For her, I will reduce this kingdom to ashes and bones.
Some flames aren’t meant to be tamed—they are meant to devour everything.