The Lernaean Hydra is a water monster from Greek mythology. It is said that the Hydra had many heads and whenever a head was chopped off, two heads will grow back in its place. The hydra had a poisonous breath and its blood was also deadly poisonous. It is said that the hero Hercules killed the Hydra with sword and fire. He protected his nose from the poisonous gas using a cloth and after cutting off a head he cauterized the open wound with fire to stop it from regenerating. Hera, who raised the Hydra then turned the dead monster into a constellation of the same name.