Chiron
One of the best known centaurs is Chiron or Cheiron, Chiron was the most important centaur in Greek mythology known as the King of Centaur, famous for his teaching ability. He was the son of the Titan god Cronus and the nymph Philyra. Although centaur had the upper body of a man and the lower body of a horse, Chiron's front legs were also human, showing that he was different and higher in class than the rest. Other differences between Chiron and the other centaur were that he was far more civilized in nature, not indulging in drinking and being overcome with lust. He had superior knowledge, and he had different lineage to the other centaurs, who were born by the union of Ixion and Nephele.
He lived on Mount Pelion with his wife, the nymph Chariclo, Three daugthers Hippe, Endeis, and Ocyrhoe; as well as a son, Carystus. He also has a lot of students included famous heroes and gods of the Greek myths such as Asclepius, Ajax, Achilles, Theseus, Jason, Peleus, and even Heracles and Phoenix.
His death was the result of events that started when Heracles visited the centaur Pholus in his cave, while trying to complete the fourth task described in the Labours of Heracles. The two individuals had dinner and Heracles asked for wine. Pholus opened a bottle of sacred wine given to him by Dionysus, but the smell attracted the other centaurs from he nearby area. The centaurs attacked in an effort to take the wine, but Heracles killed many of them using poisoned arrows. One of those arrow hit Chiron by mistake. Chiron was immortal and could not die, but the poison caused unbearable pain to him. So, he happily gave up his immortality in exchange for Prometheus' freedom, when he was asked to do so by Heracles.
In other version however, Pholus was having dinner with Heracles. After dinner was over Heracles get thirsty and decided to get himself a wine. The wine that he took, however was a sacred wine of the centaurs. It was meant to only be drunk by centaurs and only on special occasions. Pholus saw this and could not muster up the courage to tell his strong friend that he was not allowed to drink that wine. It was not long before the scent reached the other centaurs. The infuriated centaurs grabbed weapons and charged at Pholus' house. The coward Pholus fled almost immediately and left Heracles alone. Heracles killed several of the centaurs making the rest of them afraid and tried to run. Upon shooting at the fleeing centaur, Heracles' poison arrow grazed the knee of Chiron who was not involved in the fight but came out to try to stop the fight. The immortal Chiron could not die from his wound but the poison caused unbearable pain to him forever. He cried to Zeus to give him relief and end his life. Zeus took pity on the centaur and let him die. To honor him, Zeus gave Chiron a place among the stars and become the Sagittarius in the constellation we know today.
Review/Moral
I think from this brief story of his death the moral actually coming from the part where Pholus could not muster the courage to tell Heracles about the wine, if he able to tell Heracles the death of Chiron can be avoided.
Reference:
https://en.wikipedia.org/wiki/Chiron
http://www.greekmythology.com/Myths/Creatures/Chiron/chiron.html
http://www.theoi.com/Georgikos/KentaurosKheiron.html
https://atlanticreligion.files.wordpress.com/2014/06/chiron-achilles_detail.jpg
