What was the main conflict and how was it solved in The House of Hades?

In "The House of Hades," the main conflict revolves around the struggle to close the Doors of Death, which are being exploited by the forces of the Titan Kronos, threatening the world with chaos. The protagonists, Percy Jackson and Annabeth Chase, along with their friends, must journey through the Underworld to reach the House of Hades and confront the monstrous Gaea. The conflict is resolved when they successfully navigate the challenges within the Underworld, ultimately closing the Doors and preventing Gaea's resurgence. This act restores balance and allows the demigods to continue their fight against the Titans.