A war between the Titans and Olympians ensues, one that has been in the making for much of the series. In the end, Luke, who is also invincible from bathing in the River Styx, kills himself in order to send Kronos back to Tartarus. Silena Beuregard turns out to be the spy. She is a good person inside, but Luke threatens her, and they make a deal that Beckendorf will not be hurt, as she was Beckendorf's girlfriend. Silena dies trying to kill a drakon, disguised as Clarisse, which upsets Clarisse greatly.In the end of the book, Luke commits suicide to save the Olympians.