The Nemean lion is a monster that is best known for being one of the beasts fought by Hercules as one of his twelve labors. The Nemean Lion is one of the children of the faded Titaness of the moon, Selene, and Zeus, which she bore on request of Hera and fell from the moon so the latter could send it after Hercules. It is also said to have been the son of Echidna and Typhon or the offspring of Orthus and the Chimera.
In Greek mythology, the slaying of the Nemean Lion was a task given to Hercules by his cousin King Eurystheus. After hearing his description of the lion, he was able to confront it, and did not use any weapons at first; instead he strangled it to death. When he tried to cut its skin, his knife shattered, and eventually Athena told Hercules to use the lion's claws to skin it.
While Percy Jackson, Annabeth Chase, and Grover Underwood were on the train to Denver, Percy looked out the window and saw a huge lion. He thought that was weird since there are no native lions in the United States, but eventually forgot about it.
The Nemean Lion was later depicted being defeated by Hercules during a firework display at Camp Half-Blood.
The lion was sent by Luke Castellan and the General at the National Air and Space Museum to stop the group of questing Hunters, demigods, and one Satyr. It battled with Percy, who recognized the monster from the time he saw one from the train during the quest to find Zeus' Master Bolt. The monster was incredibly hard to defeat because of its bulletproof and sword-proof pelt. Zoë Nightshade and Bianca di Angelo shot arrows at it from above, but they broke harmlessly against his pelt, while Percy and Thalia were too afraid to get in close and attack with their sword and spear respectively. Percy however came up with an idea and grabbed a few packets of astronaut food from the gift shop and tossed it into the lion's mouth when he roared. When the lion bellowed in disgust, Zoë fired arrows into the Nemean Lion's only unprotected surface, its mouth. The lion dissolved except for its pelt. The pelt was offered to Percy by Zoë because it was his plan that made it possible for them to defeat the monster. When Percy was about to offer the pelt to Poseidon, Zoë asked Percy why he would offer the pelt, Percy said he is not Hercules, that seemed to surprise Zoë. The pelt was later offered to Poseidon so the Ophiotaurus could make it to Olympus safely.
The Nemean Lion is most famous for its metallic gold fur, which is impervious to damage and acts as a natural armor capable of deflecting celestial bronze weapons, Thalia's lightning, gunfire, and even the manticore's poisonous spines without harm. Only the Lion's own claws and teeth can penetrate its fur, which is how Hercules skinned it in the original myths. Despite this, there are ways to bypass the Lion's protective fur; its eyes and the inside of its mouth are vulnerable to attack when open, and while its fur protects its skeleton and organs from breakage and rupture, Hercules was still able to asphyxiate it by constricting its windpipe.
- Main article: Nemean Lion's Pelt
The Lion's spoil of war was its pelt. Percy Jackson receives this when he defeats it, as did Hercules upon completing his First Labor. When worn, it still has the same abilities of it being immune to all forms of damage. The pelt is worn around the wearer's shoulders like a cape, with the beast's scalp serving as a hood, but due to the effects of the Mist, it resembles a full-length golden brown duster to humans.
Percy describes the Nemean Lion as being "the size of a pick-up truck", with shiny silvery claws, fangs that gleam like stainless steel, and thick, glittering, metallic gold fur.
- The Nemean Lion terrorized the kingdom of Nemea, hence its name.
- Its spoil of war is mentioned in The Mark of Athena.