Kai is running out of time. He must master the catastrophic power he inherited if he wants to save his best friend from the hands of the most mercenary, most powerful merman in all the ocean, King Marius the Conqueror. The half-breed prince has never despised -or felt such intense feelings for- anyone quite as much as the Black King who once held him captive in his court. With the Spirit of the Sea's help, Kai learns the darkest of merman magic in order to fight his arch-nemesis, for Marius is coming for him.
And once he does, Kai traps Marius in a dark spell, thinking he's finally turned the tables on his once-captor. But he soon learns that Marius has power of his own, and that there's more to the Spirit of the Sea than meets the eye.
Torn between surrendering to his anger and doing his duty as Custodian of the Spirit, Kai must choose quickly, for every day that passes, more and more of the ocean is swallowed by the Dark Zones.
To save his beloved ocean, will Kai sacrifice his revenge? And can his most hated enemy turn into an ally, especially with other enemies closing in, wanting to take what's rightfully his?