Luke is first introduced in "The Lightning Thief" as the 19-year-old counselor for the Hermes cabin. He was born the year 1986. While the rest of Percy's cabin mates complain about him because he is undetermined, Luke tries to make him feel at home, even stealing a toiletry bag for him. Luke first came to Camp Half-Blood when he was 14, alongside Thalia Grace, daughter of Zeus, and Annabeth Chase, daughter of Athena. Luke has a scar on his face, a relic from his battle with the dragon Ladon, guardian of the Garden of Hesperides, while on a quest. In "The Last Olympian", it is shown that his mother attempted to become the Oracle of Delphi and has succumbed to the curse of Hades. Her crazed prophetic ramblings affected Luke greatly, and forced him to run away when he was nine. In "The Battle of the Labyrinth", Luke's body becomes the vessel that harbors Kronos' essence.
Luke dies in "The Last Olympian" when he is given Annabeth's knife by Percy. He sacrifices himself to defeat Kronos by stabbing himself under his left arm where his mortality was still kept intact after his bath in the River Styx (known as his Achilles heel). As he dies, he asks Percy to make sure all the demigods are claimed to avoid this happening again which might mean that they had become friends again because he is forgiven by Percy. Although he is seen as a villain throughout the series, in the end he is treated like a hero and forgiven by everyone. He is also the hero mentioned by the prophecy of the Oracle in "The Last Olympian".
Rachel Elizabeth Dare
Rachel Elizabeth Dare is a red haired fictional character in Rick Riordan's "Percy Jackson & the Olympians" stories. Unlike other big characters in the series, none of her parents are gods. Instead, they both are mortal. Despite this, Rachel has the ability to see through Mist, a thing that makes most humans unaware of the Olympians and immortals. She has the power to predict things, which is not common even with demigods. Because of these powers, the Oracle of Delphi passes into her from the cursed remains of the previous oracle. She therefore becomes the next Oracle of Delphi, Oracle of the Gods as well as the resident oracle at Camp Half-Blood. By becoming the Oracle, she gives up her romance with Percy because the Oracle must be a maiden. "Rats are delicious"
In this book, Rachel first appears at the Hoover Dam (in which they have a dam problem). Percy is being chased by a group of Spartoi when she sneezes. Percy turns around and his sword, Riptide, goes through her body. He realizes she knows it is a sword. He also finds out that she can see through the Mist. She saves Percy from the Spartoi by sending him into a restroom behind her and the skeletons to the generator room, which makes electricity.
In "The Battle of the Labyrinth", more details on Rachel's life are given. She shows up at Percy's new school, Goode High School. She can see that two cheerleaders are really empousai and helps Percy escape from Kelli, one of the "empousai". Later, Percy asks her to help him navigate Daedalus's Labyrinth, a maze he built, to find him. She goes with Percy and Annabeth through the maze. After finding out Daedalus has made a deal with Kronos, she escapes with Percy and Annabeth. Eventually, the three find Kronos's headquarters. Kronos has started to live in Luke Castellan's body and tries to catch Percy. Rachel appears with Annabeth and Nico di Angelo and throws her blue plastic hairbrush at Luke's eye. This confuses Kronos and lets Percy escape. She also helps find Pan, the lost god of nature. She is there when he dies.
Later, she leaves Percy, Annabeth, Nico, Grover Underwood, and Tyson. Before she does, she tells them that her father is a rich businessman who buys forests. He cuts them down and use them to build shopping malls. Pan's death affects her, mainly because of her father's job. She wants to hang out with Percy again. Annabeth is not happy about this. Percy promises to call her. He says that he has memorized her phone number. Rachel is happy about this. Percy thinks of inviting her to his birthday party. He is too afraid to do so.
Rachel and Percy become good friends in "The Battle of the Labyrinth". Annabeth becomes jealous of her. Rachel also sees that Percy and Annabeth like each other more than they will admit.
"The Last Olympian" begins with Percy driving her to the beach in Paul Blofis's Toyota Prius. She asks him to go with her and her parents on a vacation in St. Thomas, which he refuses nicely. They are interrupted by Percy's pegasus, Blackjack. He lands on the car with Charles Beckendorf riding him.
Percy goes to sink the "Princess Andromeda", a ship which Kronos is using as his base. Rachel kisses him for good luck before he leaves. In Percy's dreams, he sees Rachel writing things in Ancient Greek. She is drawing pictures of things she has never seen before, like a picture of Luke Castellan at age nine. When she goes on vacation with her parents, she asks them to return to New York by making a deal with her father to go Clarion Academy. Clarion Academy is a finishing school (a girls' school that teaches culture and social things) for girls that her mother also went to. This was all because she felt that Percy was in danger. Later on, Rachel flies to Camp Half-Blood on Blackjack. She takes in the spirit of the Oracle because Hades lifts the curse he had put on it. She says the next Great Prophecy. Rachel then goes back to the mortal world for the school year, leaving the campers without their oracle until the next summer.
Rachel's father is extremely wealthy, but she does not like the way her familly lives. She prefers helping charity. She also likes art, and sketched multiple realistic images of the past and future (sometimes things she never could have seen, like a 9-year-old Luke Castellan).
Rachel is a love interest for Percy, which created tension between her and Annabeth. However, she explains that she was attracted to Percy because he was the one who led her to her destiny as the Oracle. As the Oracle, she cannot fall in love or have children. She has respect for Annabeth and Percy's relationship.
Nico di Angelo
Nico di Angelo is a fictional character in Rick Riordan's "Percy Jackson & The Olympians," "The Heroes of Olympus" series and The Trails of Apollo. In the series, he is the demigod son of Hades and mortal Maria di Angelo. As such, Nico has extraordinary powers of necromancy and the power to command the dead; he is a son of one of the "Big Three" Greek gods, the other two being Hades' brothers Poseidon and Zeus. Nico is chronologically over eighty years old as a result of his prolonged stay in the Lotus Casino in Las Vegas, an enchanted hotel where one does not age and time does not pass at its normal pace. He was ten years old in the Titans Curse. He and his sister, Bianca Di Angelo, were placed in the Lotus Casino sometime around World War II and eventually taken out by a “lawyer” (The Fury, Alecto) when Hades commanded. He also found his half-sister Hazel Levesque in the Underworld and took her back to Camp Jupiter as she was a child of Pluto. He is currently in a relationship with Will Solace.
Nico is said to have shaggy, messy black hair, olive skin (Although it has paled over time) and dark brown eyes. After his time in the maze, he is described as having a pale complexion. He usually wears dark clothing including black ripped jeans and is also mentioned on several occasions to be wearing an aviator's jacket. By the end of "The Battle of the Labyrinth", he also wears a skull ring, a gift from his deceased sister Bianca.