The Oath Breaker

Before Taryn and Vladimir and the great war that shook the continent, the Kavari Michael Gallows sought a weapon to end his own war, and Evelyn Illdalore was destined to follow in the steps of her father but always dreamed of venturing beyond her city's walls.

A chance encounter entwined their fates, testing their loyalties and desires and awakening hopes of a different future. But the cost of love demanded more than they could ever sacrifice, and to break the binds of oaths and duty would mean forsaking everything
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The Oath Breaker explores the origin story of Taryn's parents, and while a prequel, it should only be read after finishing all four books in the Blood Vier quartet.