Amnesiac Sea God heir Lyra is forced into a political marriage with Abyssal Prince Kael, her suspected betrayer, only for their wedding ritual to reveal their lost son, Finn, alive and raised by Kael's presumed-dead brother Darian. Lyra's recovered memories expose Kael's innocence and Darian's secret sacrifice, all orchestrated by Vesper, a ruthless siren wielding ancient curses and stolen royal power to conquer the Seven Seas. Meanwhile, Finn’s unique blood awakens Neroth, an ancient, six-eyed god seeking a vessel. The family—Lyra, Kael, Darian, and Finn—must navigate choices of blood, memory, power, and sacrifice, drawing the colossal Leviathan into their war. Vesper merges with Neroth, stealing Lyra's power and transforming Leviathan into a weapon of divine destruction, yet their bodies remember, freeing Leviathan only to unleash an even older prisoner, now seeking its ancient form.
