A Chill in the Flame by Piper CJ

From the bestselling author Piper CJ comes the first in a standalone dark romantasy duology. Discover the origins of demons and darkness and uncover the twisted politics behind the sprawling, bloody continent in the Villains books, set in Piper’s beloved The Night and Its Moon universe.

Shattered by her sister’s murder, Princess Ophir’s gift for fire magic spirals in her grief, threatening to incinerate the castle. That is, until mysterious siren Dwyn arrives from the sea, pledging both assistance and something more. They work to quench Ophir’s flames, all the while Dwyn’s longtime rival watches from the shadows: Tyr, who has tracked Dwyn’s abilities across the continent and now finds himself embroiled in a sinister competition with her for Ophir’s heart.
But everything changes when Dwyn’s calculated lessons unlock a second power in Ophir, the most rare and dangerous of all magic…manifestation.
Ophir knows three things for certain. One, she burns passionately for both the beautiful siren and the rugged master of secrets. Two, with their powers combined, the trio can seek revenge against her sister’s killers.
And three, no one can be trusted.