Chiron was a centaur, known especially for his good heart and wisdom.
When Prometheus was bound and tortured at Caucasus, Chiron offered to be killed to save him. For an unknown reason, Zeus accepted him as a substitute and released Prometheus.
Chiron raised Aesculapius and taught him the practices of medicine and herbs. Aesculapius eventually surpassed Chiron, and as he became gradually more proud and godly, Zeus killed him.