Chiron

History
Chiron was sired by Kronos, who was in the form of a horse at the time. His mother, Philyra abandoned him at birth because of her disgust at his appearance. Chiron is not a true centaur, as centaurs are notorious for being overly indulgent drinkers and carousers, given to violence when intoxicated, and generally uncultured delinquents, each Centaur was also wild and lusty. Chiron, by contrast, was intelligent, civilized and kind. Also, true centaurs are born of sun and raincloud.

Throughout the Greek age, Chiron was a known teacher of heroes, including Asclepius, Aristaeus, Ajax, Aeneas, Actaeon, Caeneus, Theseus, Achillies, Jason, Peleus, Telamon, Hercules, Oileus, and Phoenix. He supposedly died, after giving his immortality to another, and then was shot with an arrow. This account is false, as Chiron lived to Percy Jackson's time.

The series
Chiron is the centaur that dwells at Camp Half-Blood as the immortal teacher to demigods. He is the son of Kronos. The prophecy involving the 16-year-old demigod to have the power to overthrow Mount Olympus is known to him. Chiron is also known as Mr. Brunner because he went under-cover as a teacher at Percy's school to teach as a Latin teacher named Mr. Brunner, who was in a wheelchair. Though he is said to be immortal, the gods decreed that he should live until he is no longer needed to train half-bloods. In greek mythology, Chiron taught many of the famous heroes such as Asclepius, Achilles and Hercules and others. He is like a father to Annabeth, who has lived at camp longer then anyone, and is also fatherly towards Percy.

In The Lightning Thief he posed as Percy's Latin teacher, Mr. Brunner. He used an enchanted wheelchair to hide his backside and used fake legs. In the muesum, he saves Percy from being killed by the Fury by throwing him Riptide. He later pretends it didn't happen, with the hopes that Percy won't notice. However, Percy isn't convinced.

Percy looks up to him, and is very upset when he thinks 'Mr. Brunner' is disappointed in him. Later, it is revealed when Percy eavesdrops on a conversation between his teacher and Grover that 'Mr. Brunner' is worried about Percy's safety and whether he is prepared or not, and does not want to get him involved yet.

That however is proved to be impossible. On the way home, Percy sees the Fates cut a cord, and Grover is terrified that they meant Percy's life. Later, Percy runs off without Grover, and they later run into camp, losing Percy's mother Sally to the Minotaur. Grover is disgraced because he was dragged across the boundry line by Percy, and was wounded at the time. The Council gives him a third chance, and tells him he hasn't exactly failed with Percy yet.

Chiron is worried about Percy, and cares for him. He tries to train Percy as much as possible, and hopes that Percy is the son of a lesser god (for Percy's own safety), though he suspects that Poseidon is in fact his father. When he is forced to send Percy on his quest, he lamants that he was unable to train him further.

In The Sea of Monsters, he is blamed for poisoning Thalia's tree and the camp's borders since he is the son of Kronos, and Tantalus took over as Activities Director. Percy and Annabeth (Annabeth especially) are furious that he is untrusted, and they do not know why Chiron is suspected, as they don't know about Kronos being his father. Before he leaves, he meets Tyson, Percy's half-brother, and Tyson takes a liking to him, calling him 'pony' which Chiron finds offenssive. Annabeth cries when Chiron leaves, and Percy feels like crying, though he won't let himself.

Percy is desperate to bring back Chiron and get rid of the evil, twisted Tantalus, and suceeds, by starting an Iris Message behind Luke, and getting Luke to admit he had poisioned Thalia's tree. Tantalus is then banished back to the Underworld (just as he managed to grab a hamburger) and Chiron and the rest of his species save Percy, Annabeth, and Tyson from Luke and his goons.

Later, Chiron comforts Percy in his mission, and reveals his parentage when Percy says he is still confused about why the Council would suspect him. After Thalia is expelled from the tree, Chiron is shocked and afraid for her, and Percy.

Because now there were two possible pawns for his father Kronos to use.

In The Titan's Curse, Chiron tries to comfort Percy after Annabeth is kidnapped. He later arranges a friendly 'Capture the Flag' game between the Campers and the Hunters. After Thalia and Percy get into a fight, Chiron breaks them up, and is amazed by seeing the Oracle coming out of the Big House and delivering a prophecy to Zoë. Later, when Percy is excluded from the rescue group, Chiron tries to comfort him, but Percy doesn't want to be comforted, it makes things worse. Chiron deeply cares about Annabeth, they are even closer to each other then Annabeth is to her actual father, and he is sure that the group will find her.

Later, after Percy realizes that Nico is the son of Hades, he hides that from Chiron, afraid of what he will do. When Percy asks about mortals that see through the Mist, Chiron informs him that some mortals are special, and can do that, including Percy's mother Sally. Percy asked because of his encounter with Rachel.

In The Battle of the Labyrinth, Chiron is slightly distrustful of Quintus, and he talks about it with Percy. He later talks about the Labyrinth with Percy and Annabeth, and the entrance that is within the boundries of the Camp, and assigns the quest to Annabeth. She is nervous, and Chiron later speaks with Clarisse about her time in it. She had been first asked to go back, but hotly refused, saying 'she would never go back to that place again'.

Chiron later speaks battle statistics with the Campers, and says that he knows where Percy was when he was missing (Calypso's Island). He was very heart-broken when Percy had been missing, and was relieved to see him again. He fights in the battle against Luke's forces, and they will, with the help of Grover.

In The Last Olympian, Chiron tells Percy of what happend with Typhon and is very worried for the fate of Olympus. He organizes the teams for battle, and fails at convincing Clarisse to fight with them. He later fights in battle against his father, and there is a confrontation between the two, and was called 'that weakling son of mine' by Kronos. Chiron is thrown against a wall and covered with rocks, and dug out by Mrs. O'Leary. He is injuried, but manages to make it to camp, where Rachel recieves the Spirit of Delphi. He is in the audience that hears the next great prophecy, and comforts Percy, Annabeth, and Rachel that it may be years before the furfillment of that prophecy.

Film
In the upcoming film The Lightning Thief Chiron will be played by Pierce Brosnan.