Lernaean Hydra. The Lernaean Hydra or Hydra of Lerna, more often known simply as the Hydra, is a serpentine water monster in Greek and Roman mythology. Its lair was the lake of Lerna in the Argolid, which was also the site of the myth of the Danaides. Lerna was reputed to be an entrance to the Underworld, and archaeology has established it as a sacred site older than Mycenaean Argos. In the canonical Hydra myth, the monster is killed by Heracles as the second of his Twelve Labors. According to Hesiod, the Hydra was the offspring of Typhon and Echidna. It had poisonous breath and blood so virulent that even its scent was deadly. The Hydra possessed many heads, the exact number of which varies according to the source. Later versions of the Hydra story add a regeneration feature to the monster: for every head chopped off, the Hydra would regrow two heads. Heracles required the assistance of his nephew Iolaus to cut off all of the monster's heads and burn the neck using sword and fire. The oldest extant Hydra narrative appears in Hesiod's Theogony, while the oldest images of the monster are found on a pair of bronze fibulae dating to c. 700 BCE. In both these sources, the main motifs of the Hydra myth are already present: a multi-headed serpent that is slain by Heracles and Iolaus. While these fibulae portray a six-headed Hydra, its number of heads was first fixed in writing by Alcaeus, who gave it nine heads. Simonides, writing a century later, increased the number to fifty, while Euripides, Virgil and others did not give an exact figure. Heraclitus the paradoxographer rationalized the myth by suggesting that the Hydra would have been a single-headed snake accompanied by its offspring. Like the initial number of heads, the monster's capacity to regenerate lost heads varies with time and author. The first mention of this ability of the Hydra occurs with Euripides, where the monster grew back a pair of heads for each one severed by Heracles. In the Euthydemus of Plato, Socrates likens Euthydemus and his brother Dionysidorus to a Hydra of a sophistical nature who grows two arguments for every one refuted. Palaephatus, Ovid and Diodorus Siculus concur with Euripides, while Servius has the Hydra grow back three heads each time; the Suda does not give a number. Depictions of the monster dating to c. 500 BCE show it with a double tail as well as multiple heads, suggesting the same regenerative ability at work, but no literary accounts have this feature. The Hydra had many parallels in ancient Near Eastern religions. In particular, Sumerian, Babylonian, and Assyrian mythology celebrated the deeds of the war and hunting god Ninurta, whom the Angim credited with slaying 11 monsters on an expedition to the mountains, including a seven-headed serpent and Bashmu, whose constellation was later associated by the Greeks with the Hydra. The constellation is also sometimes associated in Babylonian contexts with Marduk's dragon, the Mushhushshu. Eurystheus sent Heracles to slay the Hydra, which Hera had raised just to slay Heracles. 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. He shot flaming arrows into the Hydra's lair, the spring of Amymone, a deep cave from which it emerged only to terrorize neighboring villages. He then confronted the Hydra, wielding either a harvesting sickle, a sword, or his famed club. The chthonic creature's reaction to this decapitation was botanical: two grew back, an expression of the hopelessness of such a struggle for any but the hero. The weakness of the Hydra was that it was invulnerable only if it retained at least one head. The details of the struggle are explicit in the Bibliotheca: realizing 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 of using a firebrand to scorch the neck stumps after each decapitation. Heracles cut off each head and Iolaus cauterized the open stumps. Seeing that Heracles was winning the struggle, Hera sent a giant crab to distract him. He crushed it under his mighty foot. The Hydra's one immortal head was cut off with a golden sword given to Heracles by Athena. Heracles placed the head; still alive and writhing; under a great rock on the sacred way between Lerna and Elaius, and dipped his arrows in the Hydra's poisonous blood. Thus his second task was complete.