In the end of the book, Luke who is also invincible from bathing in the River Styx stabs himself as a result killing himself in order to destroy, but not kill, Kronos and therefore save the Olympians.
In the end of the book, Luke who is also invincible from bathing in the River Styx stabs himself. As a result, he kills himself in order to destroy, but not kill, Kronos and therefore save the Olympians.