The Titan's Curse

Reaching the peak of Mount Othrys, the group find Artemis holding up the sky, a role that Annabeth was also subjected to, explaining the true nature of Percy's dreams. Percy briefly takes the sky's weight, freeing Artemis. Luke tempts Thalia into joining Kronos’ forces, but she declines, knocking him off the mountainside. Percy and Artemis trap Atlas beneath the sky, but not before he casts Zoë off a cliff, mortally wounding her. Frederick flies to the rescue, piloting a Sopwith Camel, the half-bloods escaping to a nearby airfield where Zoë dies of her wounds, transformed into a new constellation by Artemis called the "Huntress".

Percy, Annabeth, Thalia, and Artemis travel to Mount Olympus to attend the gods’ winter solstice meeting, Artemis convincing the Olympians of the Titans’ threat. Bessie is kept on Olympus for safekeeping. Thalia joins the Hunters to forestall the Great Prophecy, in which a child of either Zeus, Poseidon, or Hades could be used to bring victory for Kronos. Percy learns from Poseidon that Luke is alive. Upon returning to Camp Half-Blood, Percy informs Nico of Bianca's demise. A distraught Nico blames Percy, revealing he is a son of Hades when he banishes the spartoi to the Underworld, before fleeing. Percy tells Annabeth and Grover of Nico's lineage, the trio promising to keep it a secret, fearful that Nico will be the subject of the Great Prophecy.

Characters

• Percy Jackson: Percy, a 14-year-old demigod and son of Poseidon, is the protagonist as well as the series' narrator. He embarks on a journey to save Annabeth and the Greek goddess Artemis, who have both been kidnapped.
• punk
  , with electric blue eyes, black clothes, and spiky hair. Her personality is often described as "independent and many times sarcastic." While Thalia is a lot like Percy (due to both being children of the Big Three), and they become good friends before the events of the book, they often argue. She is heartbroken by Luke's betrayal of the camp and gods, as it is implied that she had feelings for him. She is also afraid of heights, which she reluctantly admits to Percy, despite the fact that she is the daughter of Zeus, God of the Sky. She joins the Huntress of Artemis as the new lieutenant to prevent her from being the child of the Great Prophecy with the permission of her father.
• Annabeth Chase
  : Annabeth is a 14-year-old demigod and the daughter of Athena. She is friends with Percy, Thalia, and Grover. She is kidnapped, along with Artemis, by the Titans. She has a great passion and interest in architecture, and wishes to be an architect when she is older. Although she has a growing love interest in Percy, her feelings for Luke remain a problem between the two. Percy returns her feelings without realizing it, and is oblivious to how she feels about him.
• Pan
  , the satyr god of nature and the wild, who fell into a "deep sleep" due to humans' pollution of the world.
• Bianca di Angelo: Bianca is a 12-year-old demigod and the daughter of Hades
  . She and her ten-year-old brother Nico were trapped in the Lotus Casino, where time is slowed down, but at the beginning of the book, they got out and she attended an army school in Bar Harbor, Maine. She is killed by an automaton during the quest in the "Junkyard of the Gods".
• Zoë Nightshade: Zoë is the daughter of Atlas, a banished Hesperid for helping the hero Hercules, the first lieutenant of the Hunters of Artemis, and the maker of Percy's sword, Riptide. Due to her age, she often has trouble updating her language and speaking skills, and uses Middle English
  . She dies after being bitten by Ladon the dragon, who protects the immortality-giving golden apple tree, and after her father Atlas throws her against a pile of rocks. Artemis turns her spirit into a constellation soon after her death. She and Thalia developed grudges against each other after Thalia refused to join the hunters before the events of the series, but they eventually get along before Zoë's demise.
• Luke Castellan: The 21-year-old demigod son of Hermes, Luke is the main antagonist of the series. He is the main crony to Kronos
  ; Kronos' followers and army gather on a ship called the Princess Andromeda. He is thought dead when Thalia kicks him off Mount Tamalpais, but he is later revealed to have survived.
• Nico di Angelo: The 10-year-old demigod son of Hades, he and his older sister, Bianca, are rescued from a manticore by Percy, Annabeth, Thalia, and Grover. He is left at camp during the quest due to his young age, but stays in the Hermes
  cabin because his parentage has not yet been discovered. He leaves camp after hearing Percy broke his promise to him and letting Bianca die. Before he leaves, he sends an army of skeletal warriors back to the underworld, revealing his parentage.