Between Sun and Moon by Jaclyn Kot — book slip

Sage is trapped in Clearwell Castle, forced to live under the rule of a ruthless king whose tyranny has led to the deaths of many Cursed.

With her powers suppressed by an iron collar, Sage is determined to end the king's reign and stop the persecution of the children of the Old Gods.

However, her resolve is tested when she meets Prince Aurelius, the enigmatic heir to the Edenvale throne, who feels strangely familiar.

As Sage unravels the mysteries of her past, she discovers that Von, the seductive immortal she once trusted, has hidden more than just his identity from her. With the past threatening to consume her, Sage must decide whether it will forge her into someone stronger or destroy her completely.