Three books. One final year. And secrets that were buried for a reason.

Vivienne Valeran thought her last year at Erthea Academy would be about finishing her studies and figuring out what came next. Then Diego returns from Atheria with more questions than answers: an ancient sealed box that should never have left the ruins where it was found.

Vivi has spent years secretly mastering forbidden thread magic. Diego is struggling to control powers no one fully understands. When the box responds to their combined magic, it reveals the first fragments of a grimoire left behind by Ravenna, a Morvain sorceress whose mistakes once ended in devastation.

The deeper Vivi digs, the harder it becomes to know whether she's uncovering Ravenna's mistakes, or repeating them. And Diego refuses to let her face it alone, even though staying close brings its own danger. They've spent years insisting they're only friends. No one else believes it.

With the academy watching, their friends caught in the fallout, and old magic stirring beyond the walls, Vivi and Diego have to decide how far they'll go for answers, and what they're willing to lose to keep them out of the wrong hands.