Jason is a blond-haired, blue-eyed teenager with a small scar on his lip and a tattoo bearing the letters SPQR. He wakes up with severe amnesia, entirely unsure of his identity or how he arrived in Nevada. Despite his memory loss, he possesses powerful combat skills and an instinctual understanding of Roman mythology. He feels the heavy burden of leadership and the expectations of others as he tries to navigate his new reality.

Piper is a Cherokee teenager with unevenly cut brown hair and eyes that shift color. She tries to downplay her natural beauty to avoid drawing attention. Sent to the Wilderness School after using her persuasive voice to accidentally take a BMW from a dealership, she struggles with feelings of inadequacy. She faces a severe internal conflict when a mysterious voice in her dreams demands she betray her new friends to protect her family.

Leo is a petite, dark-haired teenager with a mischievous smile and a constant stream of jokes. He uses humor as a defense mechanism to hide the deep pain and guilt he carries over his mother's tragic death. A highly skilled mechanic, he is fascinated by the technology at Camp Half-Blood and the broken bronze dragon Festus. He secretly possesses the rare ability to create fire, a power he fears using.

Initially appearing as an aggressive physical education coach at the Wilderness School, Coach Hedge is actually a pugnacious satyr. He works as a protector for young demigods, always eager to fight any threat with his club. Despite his combat-ready attitude, he frequently gets distracted by his appetite for grass and furniture, though he remains fiercely loyal to his charges.

The queen of the gods, known in her Roman form as Juno. She currently suffers imprisonment by an unknown enemy and reaches out to the demigods through visions and dreams. She acts as a guiding, if demanding, force for the young heroes, orchestrating a dangerous plan to prevent a massive war.

The goddess of snow, possessing pale skin, black hair, and an icy demeanor. She views herself as superior to mortals and demigods alike. She has a persuasive ability that targets the insecurities of those around her and actively opposes her father's leniency toward the visiting heroes.

A white-haired, completely mad mortal resurrected by a mysterious patron. He resides in an opulent mansion, eager to turn anyone who crosses him into a golden statue to add to his collection. He shows absolutely no remorse for his infamous curse.

The cruel king of the wolves, possessing a horrifying face with thin skin, red eyes, and sharp teeth. He wears a crown of bones and harbors an ancient, bitter grudge against the gods, seeking to hunt down their children for revenge.

A towering, thirty-foot-tall giant who breathes fire and possesses dragon-like legs. He orchestrates a cruel blackmail scheme from his mountain lair, appearing in Piper's dreams to force her into betraying her friends in exchange for her father's life.

The imposing King of the Giants, boasting green skin and long green hair braided with weapons. He is being awakened to serve as a direct replacement for the king of the gods, drawing his massive power from an imprisoned divine source.

An ancient, resurrected princess who runs a subterranean department store. She possesses a dangerous charmspeak ability and holds deep-seated bitterness over her mythical past. She uses luxury goods and potions to eliminate wandering heroes.

Piper's father is a handsome, famous Cherokee movie star. He attempts to shield his daughter from the excesses of Hollywood and his own past struggles, but his frequent absences leave Piper feeling neglected. He remains entirely unaware of the mythological reality that shapes his daughter's life until he is targeted by dark forces.

A Hunter of Artemis with spiky black hair and brilliant blue eyes. She renounced a typical demigod life to join the goddess Artemis, taking a vow of chastity and hunting monsters. Her painful family history holds significant clues regarding Jason's lost memories and true heritage.

A blonde teenage demigod and daughter of Athena. As a senior leader at Camp Half-Blood, she is highly knowledgeable about the mythological world and guides the newcomers. She is currently deeply distressed by the recent disappearance of her boyfriend, Percy Jackson, and initially hopes the new arrivals have information about him.

A mortal oracle with curly red hair and freckles who occasionally resides in a cave at Camp Half-Blood. She has the ability to see through the Mist and serves as the vessel for the Spirit of Delphi, issuing the major prophecies that guide the campers' dangerous quests.

The vain and shallow head counselor of the Aphrodite cabin at Camp Half-Blood. She rules her cabin with an authoritarian approach, freely using her charmspeak ability to bend younger campers to her will. She takes an immediate dislike to Piper while trying to win Jason's affection.

A wise centaur with curly brown hair who serves as the director of Camp Half-Blood. He often disguises his lower half in a wheelchair when interacting with mortals. He recognizes specific aspects of Jason's past but is bound by a strict oath not to reveal the full truth to the campers.

A large, teenage-appearing immortal son of Boreus with white hair and angel wings. He lacks intelligence, missing several teeth and sporting two black eyes. He frequently asks his brother for permission to destroy any demigods that cross their path.

The immortal son of Boreus, possessing white hair styled in a feathered mullet and angel wings. He resembles a 1980s rock star and acts as a guard at his father's icy fortress, occasionally getting distracted by attractive visitors.

A brutish, hairy Cyclops who operates a workshop called Monocle Motors. He hunts wandering demigods and enjoys eating them with salsa, relying entirely on brute strength rather than intelligence during confrontations.

A muscular Cyclops who works alongside his brother at the abandoned Monocle Motors factory. Like his sibling, he is susceptible to persuasive voices but remains a dangerous physical threat to stranded demigods.

The mother of Torque and Sump, she is significantly larger and savvier than her Cyclops sons. She oversees their lethal operations and is much more difficult to trick or persuade than her offspring, posing a direct threat to Leo.

The muscular son of King Midas, bearing a scarred but handsome face. Known in mythology as the Reaper of Men, he serves as his father's personal champion and executioner, challenging guests to deadly sword fights.

A semi-transparent aura, or wind spirit, with permanently windswept brown hair. She works as the stressed personal assistant to Aeolus in his floating television studio, trying to manage his chaotic schedule before ultimately taking matters into her own hands to help the demigods.

The erratic Master of the Winds who operates a floating fortress functioning as a television studio. Constantly broadcasting the weather to satisfy the gods, the unending demands of his job and conflicting orders have driven him to the brink of madness.

A blonde-haired child of Hypnos who spends nearly all of his time sleeping. Because of his constant slumber, he has a deep connection to the world of dreams and helps others navigate the complicated nature of stolen memories.

The god of the North Wind. He operates under strict, shifting orders regarding the treatment of demigods. He balances his divine instructions from Aeolus with an interest in Jason's unique heritage and the politics of Olympus.

The god of fire and the forge. He secretly monitors his children and operates an illegal radio to communicate with them. He attempts to offer his son guidance despite the recent divine decree requiring all gods to remain silent.

The goddess of love and beauty. She watches over her children and values emotional strength over superficial vanity. She occasionally intervenes to provide essential support and insight to Piper during the quest.

The king of the gods and god of the sky, known in his Roman form as Jupiter. He has strictly forbidden the gods from contacting their mortal children. He enforces a period of divine silence across Olympus, though he occasionally answers his son's calls for help with bolts of lightning.

A ventus, or storm spirit, who masquerades as a human teenager at the Wilderness School. He is assigned as Piper's partner for a museum assignment before revealing his true monstrous nature and attacking the group on the Grand Canyon skywalk.

The head counselor of the Hephaestus cabin at Camp Half-Blood. He suffers severe injuries after doing battle with a mechanical bronze dragon that has gone awry, leaving him in a full-body cast and unable to actively lead his siblings.