In Greek mythology, The Lernaean Hydra was an ancient nameless serpent-like chthonic water beast that possessed numerous heads—the poets mention more heads than the vase-painters could paint—and poisonous breath (Hyginus, 30). The Hydra of Lerna was killed by Heracles as one of his Twelve Labours. Its lair was the lake of Lerna in the Argolid, though archaeology has borne out the myth that the sacred site was older even than the Mycenaean city of Argos, for Lerna was the site of the myth of the Danaids. Beneath the waters was an entrance to the Underworld and the Hydra its guardian (Kerenyi 1959, p. 143).
The Hydra was the offspring of Typhon and Echidna, noisome creatures of the Goddess, who became Hera. It was said to be the sibling of the Nemean Lion, yet another creature of the archaic Goddess, and thus seeking revenge for Heracles' slaying of it. As such, it was said to have been chosen as a task for Heracles so that Heracles would likely die.
Upon reaching the swamp near Lake Lerna, where the Hydra dwelt, Heracles covered his mouth and nose with a cloth to protect himself from the poisonous fumes and fired flaming arrows into its lair, the spring of Amymone, to draw it out. He then confronted it, wielding a harvesting sickle in some early vase-paintings; Ruck and Staples (p. 170) have pointed out that the chthonic creature's reaction was botanical: upon cutting off each of its heads he found that two grew back, an expression of the hopelessness of such a struggle for any but the hero, Heracles.
The details of the confrontation are explicit in Apollodorus (2.5.2): realising that he could not defeat the Hydra in this way, Heracles called on his nephew Iolaus for help. His nephew then came upon the idea (possibly inspired by Athena) of using a burning firebrand to scorch the neck stumps after decapitation, and handed him the blazing brand. Heracles cut off each head and Iolaus burned the open stump leaving the hydra dead; its one immortal head Heracles placed under a great rock on the sacred way between Lerna and Elaius (Kerenyi 1959 p 144), and dipped his arrows in the Hydra's poisonous blood, and so his second task was complete.
When Eurystheus, the agent of ancient Hera who was assigning to Heracles The Twelve Labours, found out that it was Heracles' nephew who had handed him the firebrand, he declared that the labour had not been completed alone and as a result did not count towards the ten labours set for him. The mythic element is an equivocating attempt to resolve the submerged conflict between an ancient ten Labours and a more recent twelve.
- Jane Ellen Harrison (1903) Prolegomena to the Study of Greek Religion
- Robert Graves (1955) The Greek Myths
- Carl Kerenyi (1959) The Heroes of the Greeks
- Walter Burkert (1985) Greek Religion
- Carl Ruck and Danny Staples (1994) The World of Classical Myth