Main conflict
In the novel, Gaea commands her forces to stop the demigod heroes from perusing their quest to save the world. In each of their journey's, Gaea sends monsters to kill the demigods. Percy and Annabeth encounter a great variety of monsters in Tartarus. On the Argo Two, the flying ship the majority of the demigods ride on, gets attacked by monsters and creatures as well. In the end, the goal of Percy and Annabeth and the other demigods together is to close the Doors of Death, the place where Gaea can bring back the monsters over and over.