The Erymanthian Boar (or HUS ERYMANTHIOS) was a gigantic boar, which roamed the high forest region of Mount Erymanthus in Arcadia. The third labor for Heracles was to track it down, capture and then take it back to Eurystheus. To make the task harder for the hero Eurystheus insisted the boar should be alive when it was presented to him.
Place
This animal had descended from mount Erymanthus (according to others, from mount Lampe,) into Psophis (Apollod. ii. 5. § 4; Diod. iv. 12.). Other traditions place the hunt of the Erymanthian boar in Thessaly, and some even in Phrygia. (Eurip. Herc. Fur. 368; Hygin. Fab. 30.)
Story
While making his way to Mount Erymanthus Heracles decided to visit his friend Pholus, to rest for a while before continuing his journey.
Pholus was a Centaur, he was kind and being hospitable gave food and shelter to Heracles. As Centaurs eat their meat raw Pholus cooked the share set aside for Heracles which the hero appreciated, but on asking Pholus for wine with his meal, Pholus replied that he kept only one jar, which happened to be a gift from Dionysus, and common property of all Centaurs who lived on the mountain. Heracles persuaded Pholus to open the jar, which he did reluctantly, as soon as the seal was broken the heavy aroma of strong wine drifted down through the forest. The other Centaurs caught the heavy scent from the wine, and they all came to see who had violated their precious gift. As they approached they armed themselves with rocks and stout fir branches, then attacked Heracles in an angry frenzy. Protecting himself from the melee Heracles released a volley of arrows, which drove the Centaurs into the cave of Chiron, his old teacher. Unfortunately a stray arrow hit Chiron, and as the arrows had been dipped into the poisonous blood of the Hydra, it gave him an agonizing death. Pholus also had the same fate, when one of the poisonous arrows fell from his hand penetrating his foot. Heracles could do nothing to aid his friends as the poison drained the life from both their bodies.
Full of remorse for what had happened Heracles returned to complete his task, seeking out the great Erymanthian boar, driving it from the forest up to the snow covered peaks, chasing the beast until it weakened. When the boar fell into a large snow-drift Heracles then pounced on the beast, tightly binding its feet, he then threw the boar over his shoulder and carried it back to the palace of Eurystheus.
Arriving at the palace Heracles went straight to the throne room to show the king his deed was done. On seeing the monstrous boar Eurystheus threw himself head first into a large jar, trembling with fear he begged Heracles to take the great beast away, Heracles obliged.
It must be observed that this and subsequent labours of Heracles are connected with other subordinate ones, called Parerga, and the first of these parerga is the fight of Heracles with the Centaurs.