Princess of Souls by Alexandra Christo — book slip

Selestra Somniatis has spent her life preparing to become the Somniatis Witch, bound by blood to serve the immortal King Seryth by stealing souls.

Living in a castle on the Floating Mountain, she foretells the deaths of those participating in the Festival of Predictions. But when she predicts her own death alongside soldier Nox Laederic, their fates become intertwined.

Nox, determined to take revenge on the King, forms an uneasy alliance with Selestra. Together, they must navigate a world of magic and danger to overthrow the King and escape their destined deaths.