The House of Hades

The House of Hades is the fourth book in The Heroes of Olympus series. It follows the demigod heroes Percy Jackson, Annabeth Chase, and their friends as they continue their quest to prevent the awakening of the earth goddess, Gaea. The group must navigate through the dangerous underworld, known as the House of Hades, to close the Doors of Death and prevent the monsters of Tartarus from escaping.