Sagittarius is the centaur, Chiron. Chiron was unlike the other brutal centaurs. He was kind and taught medicine, hunting, music, and prophecy. He was a wonderful teacher to many great heroes, such as Jason and Achilles, and a friend to Hercules. The latter was the one who accidentally killed the Chiron. While hunting a boar, Hercules shot Chiron in the knee with one of his poisoned arrows. Being an immortal, Chiron could not die, but Hercules promised that he would help him. This is where Prometheus comes in. Hercules happened upon him and discovered that he couldn't be freed unless someone took his place. Chiron agreed and Prometheus was set free. Chiron was allowed to die and Zeus placed his image among the stars as a reward of his noble character.