A Fire in the Flesh by Jennifer L. Armentrout — book slip

After a startling betrayal, Sera and Nyktos, the seductive ruler of the Shadowlands, find themselves captives of the false King of the Gods.

To free Nyktos and prevent a war of Primals, Sera must confront Kolis, whose erratic nature and twisted sense of honor leave her shaken.

As she navigates the cruelty of his Court, shocking truths about her duty and the realms' creation are revealed. Nyktos, determined to keep Sera alive, faces the ultimate risk of realm destruction if he doesn't Ascend as the Primal of Life.

Their destinies hang in the balance, with only an unforeseen thread more powerful than the Fates offering hope.

Third in the Flesh and Fire series, set in the Blood and Ash universe.