The fifth constellation derives its representation from the first labor of Hercules, imposed on the Hero by his cousin Eurystheus. Mythology gives different explanations for this submission of Hercules to a character much less positive than himself: in the Iliad we are told that Eurystheus had obtained power over Mycenae, and consequently over Heracles, as a consequence of a fraud perpetrated by Hera. Elsewhere we read that Eurystheus had granted Heracles permission to leave Mycenae, on condition that he first freed the country from the monsters that afflicted it. According to yet another version, the labours represented the punishment inflicted on Heracles for accidentally killing the children borne to him by Megara.
Be it as it may, the protagonist of the myth is the Lion of Nemea, the monstrous son of Ortro, himself the son of Typhon and Echidna, as well as the brother of the Sphinx of Thebes. The Lion had been brought up by Hera or by Selene, goddess of the moon, and had been placed in the territory of Nemea, where he terrified the population by eating human beings and cattle. He lived in a cave with two exits and was invulnerable. Heracles obstructed one exit, then went into the cave and strangled him, and put on his skin, using the Lion's head like a helmet.
Initially Heracles had some difficulties in skinning the Lion, because the skin was scratched neither by weapons nor by fire, but eventually he had the intuition to tear it up with the Lion's own claws and finally met with success. When he returned to Mycenae with the monster's remains, Eurystheus was so frightened by his strength that he orderded him from then on to lay his prey outside the town walls, and never to enter the city. In memory of Heracles' first deed, Zeus placed the Lion among the constellations.
The constellation is on the descending part of the ecliptic, occupies 1000 square degrees, and is placed under the feet of Ursa Major, close to the Leo Minor.