Hydra

This monster was also the spawn of Echidna and Typhon, a snake with numerous heads that were sometimes said to be human as well. It was brought up near the source of the river Amymone in order to provide a test for Heracles. The breath of the Hydra was so venomous that anyone who approached it would die, even if the monster was sleeping. Heracles thought to destroy it by cutting off its heads, but as soon as he did so more heads grew in their place. Therefore Heracles seared the bleeding necks of the monster with a torch in order to prevent growth that way. According to some legends one of the heads was immortal, but Heracles cut it off anyway and buried it deep in the earth. Heracles also dipped his arrowheads in the Hydra's blood and made them extremely poisonous. The term hydra is commonly applied to any complex situation or problem that continually poses compounded difficulties.