Hydra, << HY druh, >> was a many-headed serpent of Greek mythology. It is known as the Lernaean Hydra or the Hydra of Lerna because it lived in Lake Lerna in Argolis. One of the hydra’s heads could not die, and the rest grew back as soon as they were cut off. However, Hercules and his nephew Iolaus killed the monster by first cutting off all the heads except the immortal one and sealing each neck with fire. Hercules then cut off the immortal head of the hydra and buried it under a rock.
