Chiron was the wisest of the centaurs — a creature half man, half horse, like the rest of his tribe, but unlike them in being civilized, learned, and immortal. He was not, like the other centaurs, a son of Ixion and the cloud-Hera; he was a son of Cronus by the Oceanid Philyra, conceived when Cronus had taken the form of a horse to escape Rhea's notice. He lived in a cave on Mount Pelion in Thessaly and was the teacher of heroes: Asclepius the physician, Achilles the warrior, Jason the leader of the Argonauts, Heracles (briefly), Theseus, Aeneas (in the Roman tradition), and many others were entrusted to him in their boyhoods, and from him received the disciplines of heroic life — hunting, riding, the herbs of healing, the poems of Orpheus, the stars by which to navigate, the proper conduct of a noble man.
His death came accidentally and at the hands of the very greatest of his pupils. When Heracles had been driven to fight the centaurs (in the course of an episode at the cave of Pholus, where the centaurs had attacked over a jar of wine), one of his arrows — poisoned with the gall of the Hydra — passed through the chaos of the battle and lodged in Chiron's leg or knee. The wound was, by the Hydra's poison, both incurable and (since Chiron was immortal) impossible to die of; the centaur was condemned to suffer agony forever. He at length begged Zeus to allow him to surrender his immortality, which Zeus permitted by transferring it to Prometheus (who needed an immortal to take his place at the eagle-torment, the rotation through which finally allowed Heracles to free Prometheus). Chiron then died of his wound and was placed in the heavens as the constellation Centaurus (or, in some traditions, Sagittarius). His teaching had been the foundation of more than one heroic life; his death by accident at his pupil's hand was one of the more poignant Greek instances of the tragedy of unintended consequence.
