Prey by Cari Silverwood

To stay ‘alive’, a stoneshifter must make love to a female every ten years.
When Mila discovers her sister will be the next victim on Sacrifice Day, her normal reply would be, sorry, I’m busy.
After viewing ancient data and seeing the massive size of stoneshifters, Mila decides to rescue Tiana. Her sister is blood and she’d rather not see her tied to the sacrifice table and turned into jam.
Everything goes wrong, of course.
Lord Zarblu, stoneshifter and owner of the enormous black fortress looming over the city, turns his gaze upon Mila.
Like a giant cat with a teensy mouse, Zarblu plays with Mila. Catch…release…catch. Gentle and caring are words that no stone-beast monster should claim, surely?
Desiring something that might kill you is insane yet the sacrifice table begins to look attractive. Zarblu is a big, strong, determined male who’s had a thousand, thousand years to contemplate life.
What if he isn’t quite the monster she thought he was…
What if he wants her to be his sacrifice?