Lady of the Drowned Empire by Frankie Diane Mallis

Blindsided by their aunt's betrayal and stripped of the protections of their station, Lyr and her sisters' only hope of survival is to throw themselves into the dark intrigue of the Bamarian Court. As Meera and Morgana struggle to hide their illegal magic while living amongst their enemies, Lyr uncovers long-buried secrets from her mother that may finally unlock her power.

But the Imperators are determined to set decades-long plans into motion, with Lyr's true identity placing her at the center of their game.

As Morgana's magic intensifies to its breaking point, she comes face to face with the Lumerian Empire's most insidious secret-one that threatens her and Meera's lives.

To save her sisters, Lyr must escape Bamaria with Rhyan. Though they're being hunted by demons and tracked across borders by the Empire's forces, they're determined to solve the puzzle Lyr's mother left behind. But claiming Lyr's power may not be enough as an ancient evil returns to Lumeria.