The Hydra was a serpent with many heads in Greek mythology.
It was said to live in Lake Lerna in Argolis. For this reason , it is known as the Learnaean Hydra or the Hydra of Lerna. One of the Hydra’s Heads could not die. The rest grew back as soon as they where cut off. But Hercules and his nephew Lolaus killed the monster. They first cut off all the mortal heads. Sealing each neck with fire. Hercules then cut off the immortal head of the Hydra. He buried it under a rock.