The training ground for Greek demigods, hidden in the hills of Long Island behind a magical barrier. Run by Chiron the centaur and the perpetually aggrieved Dionysus. Most Greek demigod characters are members at some point, though belonging to the camp is always complicated by the knowledge that the mortal world cannot know it exists.

An immortal band of young women who swear an oath to Artemis, forgoing romantic love in exchange for eternal life and exceptional hunting skills. Members retain their age until they die in battle. Led at the goddess's side by a lieutenant of her choosing - a position long held by Zoë Nightshade when the Hunters first cross paths with Percy and his friends.