The Fell Queen by Camille Dwight

The Grey King’s thirst for power is sweeping the continent of Malvea, realm by realm.

Princess Neira stands as the last bastion against the forces invading her realm of Brightmere. Her father has fallen and his heir, Neira’s younger brother Ramin, won’t be spared if the walls are breached. Determined to keep the invading forces from taking over, she makes hard choices – and is betrayed by her people. Delivered to the Grey King naked and in chains, her childhood home becomes a prison in the blink of an eye.
Erqis was never the type to lead from the back – not when being at the front yields such pretty, feisty spoils. But he is not planning to get distracted by the princess. Brightmere is hiding powerful, forbidden magic, and he’s determined to destroy it before it can be used against him. At all costs, even if it means offering Neira a deal in return for her freedom.

But something sinister is lurking deep in Brightmere’s heart, and when her treacherous court falls, Neira has to rely on the king who stole her future – and become the evil queen at the tyrant’s side.