Empyrian. Empyrian Series, #1

Astrid Wahl has sacrificed everything for love. Once known as Andreas, she now stands beside Empress Viktoria of Virago as her chosen consort, her future queen, and one of the most powerful wielders of the Empyrian the world has ever known. United by destiny and bound through the mystical force that flows between them, Astrid and Viktoria have restored balance to the Empyrian and ushered in a new age of hope for their people.
But hope alone will not save a nation. As Virago struggles against a looming demographic crisis that threatens its very future, the two monarchs set their sights on neighboring Elsmere, Astrid's homeland. Bringing Elsmere into their growing empire could secure prosperity for generations and finally heal old wounds between the two nations. King Juan has other plans. Consumed by ambition and fear of Virago's rising power, the aging tyrant and his son prepare a ruthless campaign to destroy everything Astrid and Viktoria have built.
Assassination, betrayal, and war loom on the horizon as enemies move from the shadows and a deadly trap begins to close around the women who now stand at the center of history. To save their people, Astrid and Viktoria must rely upon the strength of their bond, the power of the Empyrian, and the courage to rule together against forces determined to tear them apart. Love united them. Power will test them.
The fate of nations rests in their hands. The Two Monarchs is the thrilling conclusion to the Empyrian Trilogy.