Tradition: Greek mythology
Alternative Names: Lernaean Hydra, Hydra
Category: Dragon
The Myth
The Hydra of Lerna was a monstrous, many-headed serpent that dwelt in the waters and marshes of Lerna in the Argolid. It possessed poisonous breath and blood so deadly that even its scent could kill. Its lair was a deep cave near the spring of Amymone, from which the creature emerged to terrorize the surrounding villages. The exact number of its heads varied in ancient accounts, with different traditions giving it six, nine, fifty, or simply many heads.
The Hydra was said to be the offspring of Typhon and Echidna. Its most terrible power was the ability to regenerate its severed heads. When Heracles cut off one of them, two more could grow from the wound, making the creature seemingly impossible to destroy. In some traditions it possessed a single immortal head among its many mortal ones.
The Hydra was raised by Hera for the purpose of destroying Heracles. As the second of his Twelve Labours, Heracles was commanded by Eurystheus, king of Tiryns, to slay the monster. He came to the marshes of Lerna and covered his mouth and nose against the creature’s poisonous fumes. He then drove it from its lair by shooting flaming arrows into the cave.
Heracles attacked the Hydra with his weapon, cutting off its heads one after another. But each severed head was replaced by new ones, and the monster could not be defeated while its immortal head remained. Realizing that strength alone would not overcome it, Heracles called upon his nephew Iolaus for help.
Iolaus took a burning firebrand and, whenever Heracles severed a head, cauterized the exposed neck before another could grow. Thus the regenerative power of the Hydra was finally overcome. Hera tried to save the monster by sending a gigantic crab to distract Heracles, but he crushed it beneath his foot.
At last Heracles severed the Hydra’s immortal head with a golden sword given to him by Athena. The head remained alive and writhed even after it had been cut away, so Heracles buried it beneath a great rock beside the sacred road between Lerna and Elaius. He then dipped his arrows into the Hydra’s poisonous blood, giving them a deadly venom that would later bring death to other enemies.
The Hydra’s poison continued to haunt the stories of Heracles. He used his poisoned arrows against the Stymphalian Birds, Geryon, Ladon, and the centaur Nessus. The poisoned arrow that struck Nessus ultimately led to the death of Heracles himself, as the centaur’s tainted blood was later used upon the Tunic of Nessus. The poison was also said to have contaminated the river Anigrus in Elis, whose foul-smelling waters were believed to have become poisonous because of the Hydra’s venom.
After Heracles killed the creature, Hera placed the Hydra among the stars as the constellation Hydra. The crab she had sent to aid it was likewise raised into the heavens as Cancer.
The Hydra’s regenerative heads became a symbol of an enemy or problem that only grows more difficult when attacked carelessly. The ancient Greeks even used the expression “cutting off a hydra” for a task that seemed endlessly futile, since destroying one part only caused more to appear.
Sources
“Lernaean Hydra.” Wikipedia: The Free Encyclopedia. Wikimedia Foundation. Accessed October 2, 2026. https://en.wikipedia.org/wiki/Lernaean_Hydra