Three hearts. Two Kingdoms. One dark vow.

NO ONE TOLD Thera of Erebus how heavy her late father's crown would be. But the newly appointed Shadow King feels its weight as she fights a war on two sides; against the Shadowborne, the vicious race of monsters terrorizing her people-and the vast, resourceful Luxian Empire. To end the bloodshed, the former 'soul eater' lays down her sword and forges a deal, offering to marry the Prince of Lux and settle the ages-long conflict once and for all- as long as she can keep her dark, shadowed past a secret.

No one told Prince Caelum Borealis how to lead. Cast in his father's long, impressive shadow, he has lived his days studying the texts of his people without ever seeing the action, his illness keeping him caged in his own body. But when the new King of Erebus offers him a proposition--his hand in marriage for the promise of her dark power-Caelum has the opportunity to carve his own name into the history books and finally make his late mother proud.

No one told Aurora Bellatore the true price of a life. Since she swore her oath as the youngest Captain of the Guard in Luxian history, she would gladly give her life for the kingdom of Lux-- and for her beloved Prince Caelum. But when tasked to discreetly kill the new King of Erebus, she must decide which she'd rather sacrifice; her position, or her honor.

As Kingdoms eclipse and bonds shatter, as truths come to light and betrayals are exposed, Thera, Aurora, and Caelum must make the choice to either fill the roles they've been given, or to let their hearts lead; and risk breaking them.