Persephone runs off to the Underworld with Hades, with whom she has fallen in love, but when her mother Demeter threatens to destroy the earth to save her, Persephone finds a way to come back once a year, bringing spring

Despite the warnings of her friends at Mount Olympus Academy, Persephone befriends bad-boy Hades, but following her mother's advice to "go along to get along" complicates her relationships with all of them

After learning that he is the son of a mortal woman and Poseidon, god of the sea, twelve-year-old Percy is sent to a summer camp for demigods like himself, and joins his new friends on a quest to prevent a war between the gods.

At the conclusion of The Mark of Athena, Annabeth and Percy tumble into a pit leading stragith to the Underworld. The other five demigods have to put aside their grief and follow Percy's instructions to find the mortal side of the Door of Death. If they can fight their way through the Gaea's forces, and Percy and Annabeth can survive the House of Hades, then the Seven will be able to seal the Doors from both sides and prevent the giants from raising...

Nico, the son of Hades, and his boyfriend Will, the son of Apollo, travel to Tartarus, the deepest, darkest part of the Underworld as they attempt to rescue an old friend. As the son of Hades, Nico di Angelo has been through so much, from the premature deaths of his mother and sister, to being outed against his will, to losing his friend Jason during the trials of Apollo. But there is a ray of sunshine in his life–literally: his boyfriend, Will...

When Zeus, Hades, and Poseidon continue on a new quest in the search for the Helm of Darkness, they discover many things in the Underworld that Hades does not fear except a giant three-headed dog.