He has to carry out twelve labours to become a god. One of these was to kill the hydra. The hydra was a monster with nine heads. It wasn't easy to kill. Each time he tried to cut off one of her heads,two more appeared in its place. With the help of his nephew lolaus, Hercules managed to cut of eight of heads. Then,he grabbed the ninth head and buried under a big rock. The hydra was dead.