The Lost Hero is structured as one darn thing after another. You fight the storm spirits here, battle Medea there, struggle with giants over in that corner, and maybe get teased by the snotty girl in your bunk back over that way. Each series of hurdles has its own enemies and allies and passersby. Add in the character walks-ons from other Rick Riordan books, and the name-dropping of Greek Gods and giants and Titans, and by the time you're done you've got more random characters than you can fit in your magic utility belt. We will try to list everybody below, more or less, but if there is some god, demigod, or monster missing, please chuck them into the maw of Enceladus.
Son of Poseidon; the hero of Riordan's Percy Jackson and the Olympians series. He's missing throughout this book, but he'll be important in the next volume in the series.
Daughter of Athena. She's a holdover from the Percy Jackson series too. She helps the heroes out with some advice, but is mostly looking for Percy during this book.
A mortal oracle, she foretells the future.
Centaur and adviser/counselor of Camp Half-Blood.
Son of Hypnos, god of sleep. He gives Jason some advice about his memory, and otherwise spends most of his time asleep.
Son of Iris, goddess of the rainbow.
Head of security at Camp Half-Blood; he's covered in eyes.
A son of Apollo.
A Hunter of Artemis with skill in healing.
Piper's mother; she didn't tell Piper's dad she was a goddess because she knew he couldn't handle it.
The head counselor at the Aphrodite cabin. She's a shallow jerk who torments Piper and tries to hit on Jason.
Piper's grandfather, deceased at the time of the book's opening. He told Tristan—Piper's father— many old Cherokee stories.
A son of Aphrodite who befriends Piper.
A daughter of Aphrodite, also friendly with Piper.
Former head counselor of the Aphrodite cabin, now deceased. In earlier Riordan books, she betrayed the camp during the Titan War, but then sacrificed her life to make up for her error.
Leo's father. His mom seems to have known that Hephaestus was a god. Hephaestus is shy around people. Though he thought about contacting Leo, he never did until after Leo came to Camp Half-Blood and was claimed. Leo resents him at first, but seems reconciled to him after speaking to him in a dream vision.
Leo's mother. She was a Hispanic-American mechanic and was killed in a fire caused by Gaea when Leo was eight years old. Leo blames himself for her death.
Son of Hephaestus and head of Cabin Nine. He was injured in a serious accident shortly before the beginning of the novel and is in a body cast.
A daughter of Hephaestus; she reluctantly volunteers to go on the quest until Leo asks to be chosen instead.
A son of Hephaestus and former head counselor of Cabin Nine. He died in the Titan War before the beginning of the novel.
A Hunter of Artemis and Daughter of Zeus, Thalia is Jason's full sister. She thought that their mother killed Jason when he was two by giving him to Hera. This prompted Thalia to run away from home. She dislikes Hera, whom she blames for taking Jason away.
A TV starlet who dated Zeus twice, once in his Greek aspect (giving birth to Thalia) and once in his Roman aspect as Jupiter (giving birth to Jason.) Ms. Grace was unstable, and eventually Hera convinced her to offer her Jason. This prompted Thalia to run away from home, thinking Jason was dead.
A storm spirit disguised as a mean high school boy at Wilderness School.
Tristan McClean's secretary and assistant. Piper hates her, and it turns out she is under the influence of Medea.
Goddess of snow and ally of Gaea. She hopes that when Gaea comes to power she can take the throne of her father Boreas. She has whispered bad advice to many of the gods, convincing Hera to walk into a trap, among other things. She also sends snow and storms to stop the heroes throughout their quest, and eventually fights them at the Wolf House.
God of the north wind.
Son of Boreas. He likes fighting, hockey, and pizza.
Son of Boreas. He fancies himself a lover, and is attracted to Piper.
A mean old Cyclops the heroes meet in Detroit.
One of Ma Gasket's Cyclops kids.
Another of Ma Gasket's Cyclops kids.
The ancient evil sorceress who killed her own children, brought back from death by Gaea for a return engagement. She can charm people with her voice, and also has lots of evil potions with which to wreak nastiness.
Ancient Greek king with donkey ears and the power to turn everything he touches to gold. Brought back to life by Gaea to do evil stuff.
Midas' son; a great swordfighter.
Master of the winds. He's capricious and generally not very pleasant.
An aura, or wind spirit. The heroes meet her when she is serving as Aeolus's servant. When he tries to kill them, she protects them, partially because she's fallen in love with Hedge. Eventually she takes a job as Tristan McClean's assistant, replacing Jane.
The wolf goddess who trains Roman demigods. She trained Jason, though he doesn't remember it until the end of the novel.
The first werewolf; he tries to kill the heroes.
An evil giant. He kidnaps Piper's father to try to get her to betray the quest.
The evil giant who Gaea is trying to raise to destroy the gods.