Perseus "Percy" Jackson
The protagonist of the story, twelve-year-old New Yorker Percy Jackson is the demigod son of Poseidon. Due to his half-godly Greek heritage, Percy is dyslexic and has ADHD. He is reported to have black hair and green eyes. While he lacks his friend's intelligence, Percy has loyalty and bravery, which is constantly shown in the book. Because he is the son of Poseidon, his primary weapon is Riptide (or Anaklusmos), a sword gifted to him by Chiron.
Annabeth Chase
A deuteragonist, Annabeth Chase is the demigod daughter of Athena. Because of her familial conflicts, she ran away at the age of seven before she stayed at Camp Half-Blood, a refuge for demigods. She helps Percy on his quest to retrieve Zeus' lightning bolt, using her intelligence to guide them to their destination. She is reported to have blonde hair and grey eyes, and is especially skilled with the dagger.
Grover Underwood
A deuteragonist, Grover Underwood is Percy's best friend who joins him and Annabeth to retrieve Zeus' lightning bolt. He was previously tasked to protect Percy, and prior to meeting him, Grover was tasked to find Thalia Grace, Annabeth, and Luke Castellen. Grover is a satyr - half-goat, half-human - and he can be occasionally timid. However, he does have a sense of loyalty. He weapon of choice is a reed flute, which can manipulate plants.
Chiron
Chiron trains campers at Camp Half-Blood, and for a time, he went under the alias of Mr. Brunner, Percy's Latin teacher.
Hades
Hades is the god of the Underworld and presumed to be the one who stole Zeus' lightning bolt in an effort to start war. He is portrayed as an evil god who is self-serving. It is revealed later that his Helm of Darkness was stolen, and he mistakenly believed that Percy stole it. Percy retrieved it along with the lightning bolt.
Luke Castellen
The true antagonist of the story, Luke Castellan is the demigod son of Hermes. He is portrayed as a jovial person, but he is upset at his father and desires revenge by stealing the lightning bolt and the Helm of Darkness. He proclaims himself to be the ultimate follower of Kronos, the Lord of the Titans.
Mr. D
Dionysus, the God of Wine, who was put in charge of Camp Half-Blood in an attempt to get him to have a positive influence on youth. Typically grumpy and snarky.
Kronos
Trapped in the Pit of Tartarus for the duration of the story, Kronos is this novel’s hidden antagonist, coercing Luke to do his bidding and steal the master bolt. Kronos is a Titan, imprisoned by Zeus, his son, during the war between the gods and Titans.
Poseidon
Percy’s father, the Sea God. Poseidon is one of the Big Three, and he made a vow with Hades and Zeus not to father any more children. As such, he did not claim Percy as his son until later in his life, when Percy came to Camp Half-Blood for the first time.
Sally Jackson
Percy’s mother, who is caring, sweet, and loves Percy with all her heart. She fell in love with Poseidon and had Percy, and then married a terrible man named Gabe to try to keep Percy’s demigod scent hidden from the monsters. The Minotaur seemingly kills her early in the book, but it is revealed that she was actually taken hostage by Hades.
Gabe Ugliano
Percy’s stepfather, a terrible man whom Sally married in order to conceal Percy’s scent from the monsters. He treats both Sally and Percy horribly.
Zeus
God of the Sky and owner of the master bolt, the object whose theft catalyzes Percy’s quest. Zeus is temperamental and proud, and it is best not to cross him.
Athena
Annabeth’s mother, the Goddess of Wisdom and War. Athena and Poseidon are typically rivals, and she takes Zeus’s side in the budding war between Zeus and Poseidon.
Hermes
The messenger god, father of Luke and many other Camp Half-Blood demigods.
Apollo
God of Music and the Sun, father of many Camp Half-Blood campers.
Artemis
Apollo’s twin, Goddess of the Moon and the Hunt. Artemis swore to remain a maiden forever, so she has no children; however, she has an honorary cabin in Camp Half-Blood anyway.
Hera
Goddess of Marriage and Queen of the Gods, Zeus’s wife. She has an honorary cabin in Camp Half-Blood.
Ares
God of War, father of Clarisse and other campers at Camp Half-Blood. In his human form, Ares is a strong biker who wears leather. Ares manipulates Percy into doing his bidding, and he has a role in the master bolt theft, hoping to start a war.
Aphrodite
Goddess of Love and Beauty. Technically she is married to Hephaestus, but she has been cheating on him with Ares for a long time.
Hephaestus
God of Fire and Metalworking, and father of many campers at Camp Half-Blood. He sets a trap in the water park to catch Ares and Aphrodite together, but Percy and his friends get caught in it instead.
Aunty Em
Medusa, the Gorgon with snakes for hair who can turn people into stone. She poses as an innocent owner of a garden gnome emporium and tries to kill Annabeth to get revenge because of her mother, but Percy ends up killing her–just like his namesake, Perseus.
Clarisse
Daughter of Ares, who quickly becomes Percy’s enemy at camp after trying to flush his head in the toilet.
Mrs. Dodds
One of the Furies, who is initially Percy’s math teacher but then attacks him on a school field trip, working for Hades.
Pan
A satyr god of nature who disappeared without a trace. Many satyrs, including Grover, dedicate their lives to searching for him, but so far none have returned.
Charon
The ferryman of the Underworld, who takes the dead across the River Styx. He is initially reluctant to let Percy and his friends cross because they are still alive, but ultimately he succumbs to their bribe.
Cerberus
The three-headed dog who guards the Underworld, and takes a liking to Annabeth.
Crusty
Owner of the water bed palace in Los Angeles, where Annabeth and Grover are almost stretched to death. His real name is Procrustes.
