The Battle of the Labyrinth

The Battle of the Labyrinth is a 2008 fantasy-adventure novel based on Greek mythology and the fourth novel in the Percy Jackson & the Olympians series by Rick Riordan. Fictional demigod Percy Jackson, who is fifteen years old by the end of the book, tries to stop Luke Castellan and his army from invading Camp Half-Blood by navigating Daedalus's labyrinth. It was released on May 6, 2008 in the US and Canada.

Plot summary
After being attacked by Empousai cheerleaders at his new school, Percy returns to Camp Half-Blood and learns about the "Labyrinth", part of the palace of King Minos in Crete that, according to Greek mythology, was designed by Daedalus. He also meets the camp's new sword master, Quintus, who is later revealed to be Daedalus. During a game against giant scorpions at the camp, Annabeth and Percy accidentally find an entrance into the Labyrinth. Percy soon learns that Luke had used this entrance before and will try and lead his army through the Labyrinth straight in to the heart of Camp Half-Blood.

Using the Labyrinth, Percy, Annabeth, Grover, and Tyson must find Daedalus so that Luke cannot get Ariadne's string, thereby foiling Luke's invasion. Ariadne's string is used to navigate the Labyrinth. Percy and his friends encounter Kampe, a half woman, half-dragon monster, and free her captive, Briares the Hundred-Handed One, who is Tyson's idol but disappoints him by being too scared to help them. After an encounter with the goddess Hera and a battle on the farm of Geryon, the group are reunited with Nico di Angelo, son of Hades, who still hates Percy for the death of his sister Bianca, but is convinced to put it behind him by the summoned ghost of his sister. Following a hint from the Greek God Hephaestus, Percy travels to Mt. St. Helens, where he finds telekhines, which Percy calls "sea demons". Percy attacks the telekhines and they chase him. Percy finds Annabeth and they have a short argument during which Percy tells Annabeth to flee. They kiss, and Annabeth disappears. In an attempt to escape the telekhines, Percy causes Mt. St. Helens to erupt, draining his energy in the process. After being treated for burns by Calypso, Percy gets the help he needs from a mortal girl named Rachel Elizabeth Dare, who is able to see through the Mist. Grover also finally finds Pan, but the god of the wild is dying and wants Grover to tell the other satyrs that they must save the natural world themselves - his spirit passes into all present (Grover in particular) when he dies. They finally discover that Quintus, the mysterious new sword instructor at Camp Half-Blood, is actually Daedalus (who has attained a sort of immortality by putting his life-force—his animus into a robot body) and that Kronos has gained a body by possessing Luke. Kronos finds out that Nico di Angelo is a son of Hades and also could be the child of the big prophecy. Luke has already reached Daedalus and got Ariadne's string. Using the magical instrument, he leads his army and attacks camp. Grover comes to the rescue and causes a Panic to scare away the enemy. After the battle, Daedalus sacrifices himself to close the Labyrinth, which is tied to his life.

Major characters

 * Percy Jackson: 14 years old (turns 15 in the last chapter), who is a son of Poseidon, God of the Sea. He is the series' narrator and protagonist. He joins Annabeth in her quest to go into the labyrinth to find Daedalus' workshop. He shows some interest in Calypso when he washed up on her island, but refuses her offer to stay with her (making him immortal) because he feels obligated to help his friends.
 * Annabeth Chase: 14 years old, one of Percy's closest friend and daughter of Athena. She gets the quest to navigate the labyrinth. Her feelings for Percy start to show but is confused because of her lingering feelings towards Luke.
 * Rachel Elizabeth Dare: A mortal who can clearly see through the Mist. Her father is a wealthy businessman who buys the undeveloped land of the wild and builds developments upon them. She hates her father for doing so and was embarrassed to meet Pan, God of the Wild. Percy had previously met her at the Hoover Dam in The Titan's Curse, where she helped him get away from the undead warriors.
 * Nico di Angelo: Son of Hades. Upset that his sister Bianca died, he is slightly psychotic, and attempts to trade Daedalus' soul for that of Bianca. He has a sword made of Stygian Iron.
 * Luke Castellan: Son of Hermes and traitor to the Olympians. His body becomes possessed by the spirit of Kronos. He is the series' main antagonist.
 * Grover Underwood: A satyr and Percy's best friend. His life's ambition is to find Pan, the lost God of the Wild. Grover, Tyson, Percy, Annabeth, Nico and Rachel find Pan inside a crystal cavern along with some extinct animals. He gave them words of wisdom, and then died. When he died, his essence entered all of the characters' mouths, meaning a piece of the wild remained in their hearts. He gave Grover the famous battle cry, panic, which Grover used to scare off the intruders in Camp Half-Blood. The word panic is named after Pan because in the Titan war he let out a horrible cry that drove all the monsters back to where they came from.
 * Tyson: Percy's cyclops half-brother. He now works for his father in the Palace of Poseidon under the oceans in the Cyclopes' Forge. Tyson enjoys forging, nicknaming mythical creatures they come across and eating peanut butter sandwiches. He joins Percy and his friends in the labyrinth.
 * Daedalus/Quintus: The creator of the Labyrinth and son of Athena, who makes five automatons to cheat death. He becomes the new swordsman at Camp Half-Blood under the name Quintus. He has a murderer's mark on his neck branded by Athena because he killed his nephew, Perdix. He owns a Hellhound named Mrs. O'Leary. After his death, he builds toll-ways and other buildings to control traffic in the Underworld and according to Nico, Daedalus is very happy with this job. Before he dies, he gives Annabeth a laptop containing all of the works he never had time to accomplish as well as many of his ideas and theories.

Critical reception
The Battle of the Labyrinth received generally positive reviews. Publishers Weekly praised Riordan by saying, "One of Riordan's strengths is the wry interplay between the real and the surreal", and adding that "The wit, rousing swordplay and breakneck pace will once again keep kids hooked." Children's Literature said, "Riordan creates a masterful weaving of Greek mythology and traditional fantasy in this latest book in "The Olympians" series. Fans will enjoy the latest adventures of their favorite characters, and those picking the book up for the first time will have no trouble falling into this magical world." School Library Journal wrote that  "[l]ike many series, the "Percy Jackson" books are beginning to show the strain of familiarity and repetition",  before adding "However, the overarching story line remains compelling, and the cliff-hanger ending will leave readers breathless in anticipation of the fifth and final volume." Kirkus adjudged the book to be the best in the series and said, "The often-philosophical tale zips along with snappy dialogue, humor and thrilling action, culminating in a climactic battle between gods and Titans."

Awards and nominations
Kirkus Reviews and Publishers Weekly gave The Battle of the Labyrinth a starred review. It also won the Wyoming Indian Paintbrush Book Award.

Audiobooks
The Battle of the Labyrinth was adapted to a 10 hours and 32 minutes audiobook read by actor Jesse Bernstein and published by Listening Library. The release date for the audiobook was May 13, 2008.

AudioFile Magazine was generally positive about the audiobook. They commended Bernstein, saying that he was "just as skillful at wringing humor from the witty dialogue and from the contrasts between the modern and ancient worlds."

Sequel
The Last Olympian was released May 5, 2009. It is the last book of the series.

Percy and his friends defend Olympus once more against Kronos and his forces. Percy rallies the demigods and many of his allies take part in the war, including The Hunters of Artemis and the Party Ponies. Rachel becomes the new Oracle and spouts another Great Prophecy, while Percy and Annabeth start going out.