Ten years after the Isle of Locke was destroyed and vanished beneath the sea, magic across the war-torn nation of Idistra is fading, and rumors persist that one heir to Locke's power survived. Hand Captain Grey Flynn has sworn her life to her mage, Captain Kier Seward, serving as his blade, healer, and protector, bound to him through a forbidden ritual that makes her the living conduit for his magic.
When a mission to safeguard a captured enemy child pulls Grey and Kier into the brutal heart of their nation's war, the truths they have both hidden come to light: Grey is not merely a mage's well, but the last living heir of Locke, the drowned island that is the root of all power. If she dies, magic dies with her — and as enemies and allies alike close in, she and Kier must decide what they are willing to sacrifice to protect her secret, their bond, and their world.