Percy (Perseus) Jackson and his friends fight in a war resembling the original war between the Greek gods and the Titans, and in a final battle with the powerful Titan, Lord KronosTyphon (a colossal monster that nearly destroyed Olympus in the first war) is released from under Mount St. Helens, forcing the gods to leave to fight with Olympus virtually undefended. Seeking to defeat Kronos, Percy bathes in the River Styx, like Luke, to make his body invulnerable except in one spot (mortal point; in Percy’s case, the small of his back). Percy and his friends then fight in a last stand to protect Mount Olympus from the oncoming invasion of Kronos.