The story of Hydra revolves around the tale of the second of Hercules' labours. Hydra was a gigantic dog-like beast with many heads. In order to slay the creature, Hercules had to sever the single immortal head. But each time Hercules cut off one of the heads, two more grew in place. Some stories tell of as many as thousand heads! Hercules relied on the help of his nephew Lolaus, who set fire to a grove, burning the stump of each wound to prevent the heads from re-growing. Hercules eventually found and severed the immortal head, killing Hydra.