| The |
Baby Dragon | Guardian of the Golden Fleece |
| Silena |
Beauregard | Demigod from Aphrodite cabin |
| Charles |
Beckendorf | Demigod from Hephaestus cabin |
| Paul |
Blofis | Sally Jackson's partner |
| Erymanthian |
Boar | Giant wild boar |
| Sopwith |
Camel | Aircraft |
| Luke |
Castellan | Former friend turned pawn of Kronos |
| Annabeth |
Chase | Percy's best friend and daughter of Athena. Aka: Wise Girl / Nobody |
| Bobby |
Chase | Annabeth's half-brother |
| Frederick |
Chase | Annabeth's father. Aka: Dr. Frederick Chase |
| Helen |
Chase | Annabeth's stepmother |
| Matthew |
Chase | Annabeth's half-brother |
| Santa |
Claus | Compared to Artemis's chariot |
| Rachel Elizabeth |
Dare | Mortal who sees through the Mist |
| Oracle of |
Delphi | Spirit that gives prophecies |
| Bianca |
di Angelo | Daughter of Hades |
| Nico |
di Angelo | Son of Hades and Bianca's younger brother |
| The |
Fates | Controllers of destiny |
| Mrs. |
Gottschalk | Teacher at Westover |
| Thalia |
Grace | Annabeth's demigod friend and daughter of Zeus |
| The |
Hunters of Artemis | Maiden followers of Artemis |
| Percy |
Jackson | The protagonist, a demigod son of Poseidon. Aka: Seaweed Brain / Perseus |
| Sally |
Jackson | Percy's mother |
| Clarisse |
La Rue | Daughter of Ares |
| Nemean |
Lion | Mythical lion |
| Zoe |
Nightshade | Leader of the Hunters of Artemis |
| The |
Satyrs | Creatures searching for Pan |
| Connor |
Stoll | Leader of Hermes cabin |
| Travis |
Stoll | Leader of Hermes cabin |
| Dr. |
Thorn | Teacher at Westover and a monster in disguise |
| Helen of |
Troy | Mythological figure |
| Gabe |
Ugliano | Percy's abusive ex-stepfather |
| Grover |
Underwood | Percy's best friend and a satyr |
| Skeleton |
Warriors | Animated skeleton fighters |
| The |
Wood Nymphs | Tree spirits |
| Aigaios |
| Ancient water spirit |
| Apollo |
| God of archery and Artemis's twin |
| Ares |
| God of war |
| Argus |
| Camp Half-Blood guard |
| Ariadne |
| Dionysus's wife |
| Artemis |
| Goddess of the hunt and maidenhood |
| Athena |
| Goddess of wisdom and Annabeth's mother |
| Atlas |
| Leader above Luke. Aka: The General |
| Backbiter |
| Luke's sword |
| Bessie |
| The cow serpent |
| Blackjack |
| Black pegasus |
| Chiron |
| Camp Half-Blood activities director |
| Chuck |
| Bronze angel |
| Demeter |
| Goddess of harvest |
| Dionysus |
| Camp Half-Blood director. Aka: Mr. D |
| Dracaenae |
| Dragon women |
| Gaia |
| Primordial earth deity |
| Guido |
| Pegasus |
| Hades |
| God of the underworld |
| Hank |
| Bronze angel |
| Harpies |
| Monsters allied with Kronos |
| Helios |
| Former sun god replaced by Apollo |
| Hellhounds |
| Monsters allied with Kronos |
| Hephaestus |
| God of fire and invention |
| Hera |
| Queen of Olympus |
| Hercules |
| Mythological hero |
| Hermes |
| Messenger god and Luke's father |
| Hesperides |
| Sisters of Zoe |
| Hippocampi |
| Sea horse creatures |
| Iris |
| Goddess of the rainbow |
| Kronos |
| Titan and main antagonist |
| Ladon |
| Mythical dragon |
| Laestrygonians |
| Giants allied with Kronos |
| Medea |
| Betrayed by heroes |
| Medusa |
| Woman who turns people to stone |
| Naiads |
| Water nymphs living in Camp Half-Blood lake |
| Nereus |
| Old man of the sea |
| Oceanus |
| Ancient water spirit |
| Ouranos |
| Primordial sky deity |
| Pan |
| God of nature |
| Paris |
| Mythological figure |
| Persephone |
| Goddess of flowers |
| Phoebe |
| Hunter of Artemis |
| Pleione |
| Zoe's mother |
| Porkpie |
| Pegasus |
| Poseidon |
| Percy's father and one of the Big Three |
| Riptide |
| Percy's sword |
| Selene |
| Former moon goddess replaced by Artemis |
| Talos |
| Bronze automaton |
| Theseus |
| Son of Poseidon |
| Tyson |
| Percy's cyclops half-brother |
| Zeus |
| Thalia's father and one of the Big Three |
| Zombies |
| Resurrected dead |
