The origins of the Nemean lion differ on the sources. Hesiod makes him the offspring of Orthus and a “she”, usually believed to be Chimera, though others interpret it as Echidna. He was raised by Hera and sent to terrorize the hills of Nemea. According to Apollodorus, he was The first of Heracles’ twelve labours, set by King Eurystheus (his cousin), was to slay the Nemean lion.
Heracles wandered the area until he came to the town of Cleonae. There he met a boy who said that if Heracles slew the Nemean lion and returned alive within 30 days, the town would sacrifice a lion to Zeus; but if he did not return within 30 days or he died, the boy would sacrifice himself to Zeus. Another version claims that he met Molorchos, a shepherd who had lost his son to the lion, saying that if he came back within 30 days, a ram would be sacrificed to Zeus. If he did not return within 30 days, it would be sacrificed to the dead Heracles as a mourning offering.
While searching for the lion, Heracles fetched some arrows to use against it, not knowing that its golden fur was impenetrable; when he found the lion and shot at it with his bow, he discovered the fur’s protective property when the arrow bounced harmlessly off the creature’s thigh. After some time, Heracles made the lion return to his cave. The cave had two entrances, one of which Heracles blocked; he then entered the other. In those dark and close quarters, Heracles stunned the beast with his club. During the fight, the lion bit off one of his fingers. He eventually killed the lion by strangling it with his bare hands.
After slaying the lion, he tried to skin it with a knife from his belt, but failed. He then tried sharpening the knife with a stone and even tried with the stone itself. Finally, Athena, noticing the hero’s plight, told Heracles to use one of the lion’s own claws to skin the pelt.
When he returned on the thirtieth day, carrying the carcass of the lion on his shoulders, King Eurystheus was amazed and terrified. Eurystheus forbade him ever again to enter the city; in the future, he was to display the fruits of his labours outside the city gates. Eurystheus warned him that the tasks set for him would become increasingly difficult. He then sent Heracles off to complete his next quest, which was to destroy the Lernaean hydra.
Heracles wore the Nemean lion’s coat after killing it, as it was impervious to the elements and all but the most powerful weapons. Others say that Heracles’ armour was, in fact, the hide of the Lion of Cithaeron. the offspring of Typhon.