1. Heracles convinced Pholus to open a jar of wine given to the centaurs by Dionysus, attracting the other centaurs who became drunk and attacked without understanding wine needs to be diluted. 2. During the ensuing fight, Heracles used poisonous arrows that killed Pholus and injured Chiron, though Chiron was immortal. 3. To relieve his pain, Chiron volunteered to give up his immortality to take the place of Prometheus in Tartarus.