Percy – Poseidon’s son. Again we are faced with the unknown prophecy involving Percy. But after arriving at camp this year, it is determined that a bunch of folks are headed to look for the Labyrinth created by Daedalus. Percy continues to have lots of dreams which let him see what’s going on with his enemies and others.
Annabeth – Finally chosen to lead a Quest of her own. She is headed into the Labyrinth to try to find Daedalus and Ariadne’s String (which Luke is also looking for so that he can invade the camp and start the war with the Gods and complete the rising of Kronos). She is antagonistic towards Rachel, who ends up involved since Rachel can see through the mist, and can also see the correct ways through the maze.
Grover – After the incident where he smelled Pan he too heads into the Labyrinth convinced he can find Pan. He has also been given a week by the Council of Cloven Elders a week to find evidence or he will loose his searchers license.
Tyson – Percy’s half-brother and cyclops. He seems like a child although he is in fact very smart and tough. He also crafts wonderful things, like Percy’s shield. He and Grover are leery of each other, but at one point, end up going off together.
Nico – Found early on speaking to a ghost king (who turns out to be Minos) and is looking for a way to bring back his sister from the dead. He has learned to navigate the labyrinth, to some extent, and has learned a lot about his powers and the dead. He hates Percy, but when Percy finally manages a way for Bianca’s ghost to show itself to Nico, Bianca convinces Nico that her death was not Percy’s fault. At the end, there is a truce between Percy and Nico, although Nico won’t stay in camp because he tells Percy he doesn’t really belong (and notes that there is a reason the cabins don’t include a cabin for the children of Hades).
Luke – unfortunately, he manages to bring Kronos back to life here. Kronos binds himself to Luke’s body and takes over. It’s not clear if Luke is in there too or not. Either way… Luke is bad stuff at the end.
And, again, everyone else, including Chiron, Mr. D., Luke, etc. from the first books
Rachel Elizabeth Dare – Percy runs into her again at the beginning of the new school year. Turns out there are some monsters there and they attack (one is in the form of a killer cheerleader). Percy needs to get her involved and have her join their quest since she is the only one who can navigate the maze. She is very accepting of the group and gets them all a ride home because her father is some unknown/unnamed rich big shot. I put here here because while we met her briefly in The Titan’s Curse, we really get her story for the first time in this book.
Quintas/Daedalus – Yep. One and the same. Seems Daedalus figured out how to move his spirit from his body into a robot body. He sacrifices himself so that the Labyrinth dies, since their life forces are tied together.
Pan – Grover does in fact find him. But Pan has been hanging around waiting for Grover so he can finally die. He asks Grover to tell everyone, all the other Satyrs and nature spirits to save the Wild.
Main Premise: Again the demigods need to save the camp and the world. This time it is by going into the Labyrinth to keep Luke from finding the string which will navigate him through the maze and let him attack the camp and get to Olympus. Luke finds the string and gets himself to the camp. At the end, the heros manage to save the camp – but that only delays Luke/Kronos’s “final” attack.
Locations: The Labyrinth (which is under various parts of the USA), Camp Half Blood (Long Island, NY), all the places they pop up from the Labyrinth in
Other Important Things to Remember Later: Percy woke something under Mt. St. Helens. The sea demons (telekhines) are out to get their Ocean back and Posideon is focused on that battle. Luke is possessed by Kronos. Percy rescued Ethan Nakamura from the arena in the Labyrinth. Clarisse nurses back to health a boy who went crazy in the Labyrinth. Posiedon gives Percy a sand dollar for his birthday at the end. Rachel and Annabeth really don’t like each other but Rachel is pretty well informed as to what is going on in the world around her and the existence of the gods. And a reader would have to be blind to not see she is going to be important later.