A daughter of Zeus who was transformed into a pine tree to save her life and restored as a teenager. Her existence violates the oath of the Big Three. Eventually joins the Hunters of Artemis to avoid the Great Prophecy falling to her. Jason Grace's elder sister.

Nico di Angelo's older sister, a daughter of Hades. Chooses to join the Hunters of Artemis rather than remain in the demigod world, a decision that haunts Nico for the rest of the series. Dies during the quest in The Titan's Curse.

Lieutenant of the Hunters of Artemis and one of the oldest demigods still living, having served Artemis for millennia. Daughter of Atlas. Heroic, proud, and tragic - her arc in The Titan's Curse ends with her death and transformation into a constellation.