A snake-like monster, living at Lerna in the Argolid, with numerous heads, which Herakles had to destroy as his Second Labour. As fast as the hero cut off one head, another (or two more) grew up in its place. Herakles therefore enlisted the aid of his companion and charioteer Iolaos, who used firebrands to cauterise each stump severed by Herakles, until eventually the monster was slain. In later classical art the creature is given a human head. Its blood was poisonous and Herakles kept some to tip his arrows; in early scenes Athena is shown holding a small flask for it.
Above left: Detail from an Athenian red-figure clay vase, about 450-500 BC. Palermo. Regional Archaeological Museum V763. © Palermo. Regional Archaeological Museum
Above right: Herakles attacking Hydra. Cretan coin. Obv. c. 352 BC. Paris © Kraay and Hirmer pl.167,552