The Hydra

The Hydra, which was also called Lernaean Hydra, is a nine headed sepent-like monster from Greek and Roman mythology. It wasn't just in the Greek and Roman mythology that it appears, it has many parallels in near ancient eastern religions too, like Babylonian, Assyrian and Sumerian mythology. It was also associated with Bashmu (the venomous snake) constellation (even though it only has a single head) and with the constellation from the Babylonian Marduk's dragon (the Mushhushshu).

It is the child of Typhon and Echidna. The Hydra lived in the lake Lerna in the Argolid, under this lake was the entrance to the Greek and Roman underworld which it guarded.

It is said that when you cut the a head off of the Hydra, two more will grow back, it also has poisonous breath, blood do virulent that even it's scent was deadly and the middle head was said to breath fire.

Heracles (Greek) or Hercules (Roman) was sent by Eurystheus to kill the Hydra in the second of his twelve labours. Hera raised the Hydra just so that it could kill Heracles one day, but in the mean time it would come out of it's cave to terrorise the near by villages. On entering the area where it lived, Heracles had to cover his mouth and nose with a cloth to protect against the poisonous fumes. To confront the Hydra he first had to shoot flaming arrows into the Hydra's lair from there he wielded his weapon, being anything from a harvesting sickle (from very early renditions on vase-paintings) to a sword or his very well known club. He began to cut off the Hydra's heads, but as we know they grow back, which would have dishearten anyone but our hero. The Hydra is invulnerable but only if it still has it's one immortal head, so in one version Heracles enlisted the help of his nephew Iolaus who figured out that if they used a firebrand to scorch the neck stumps right after each decapitation then they couldn't grow back (this was possibly inspired by Athena). So Heracles would cut off the heads and Iolaus would cauterize the necks. Seeing that Heracles was winning, Hera sent a large crab to distract him, who crushed it with his mighty foot. Once the immortal head of the Hydra was cut off (which is mostly known to be cut off with a golden sword given to him by Athena) he placed the still alive and writhing head under a giant rock on the sacred way between Lerna and Elaius. Heracles would then dip his arrows in the Hydra's poisonous blood to be used later in his other labours.

The alternate version is that after cutting off one head Heracles would then dip his weapon in it's neck and use it's own venom to burn the wound so it couldn't grow back. Hera, being upset that both her creatures where slain, raised them up and placed them in he dark vault in the sky turning them into constellations.