The Demon King's Impossible bride

Reborn in a fragile human body, snake shifter Seraphina must absorb supernatural heat to survive. Her perfect match is Caspian, the demon king whose molten touch kills every woman who approaches him. While the court expects her to burn, she craves his fire, wins his trust, and rises from maid to queen. But Seraphina is also an assassin sent by the Crimson Empire. When her secret is exposed, she must choose between the empire that raised her and the monster who would burn the world for her.