Chiron (Pronounced Kai-RON/ˈkaɪrən/; also Cheiron or Kheiron; Greek: Χείρων “hand”) was a centaur, but unlike other centaurs, he was directly descended from the titan Cronus. Cronus had disguised himself as a horse to seduce Philyra (an Oceanid sea nymph) so his wife Rhea would not discover the affair. As an interesting side note, Rhea was also Cronus’ sister.
In traditional Greek depictions, Chiron was initially shown as being a full man with only the hindquarters of a horse. He thrived under the tutelage of his foster-father Apollo. He was highly intelligent having mastered such skills as the healing arts of medicine, music, archery, hunting, and even prophecy. Being the son of a titan, he was immortal, and therefore certainly had a lot of time on his hands.
Chiron was very unlike his Centaur brethren who where notoriously wild, and lusty partiers that while intoxicated were given to bouts of intense violence. He excelled, was civilized and kind, and because of his less war-minded ancestry, Chiron was a tutor to heroes. Heroes he took under his wing include Achilles, Asclepius, Heracles (later known as Hercules), Jason, Aeneas, and Peleus.
Unfortunately immortality in this case does not mean forever. During a skirmish with the wild centaurs over some sacred wine, Heracles accidentally wounded him with an arrow that had Hydra blood poisoned tips. According to one version, to be rid of the unrelenting pain of the wound, Chiron gave his immortality to the titan Prometheus and allowed himself to die. According to another, he appealed to Zeus and was transformed into the constellation Centaurus the zodiac for Sagittarius.