After Hercules killed the lion Leo, he wrapped the lion's skin around him and left to kill Hydra, the water monster. Hydra had nine heads, one which was immortal, meaning it could never die, and breath that would kill what ever it came into contact with. He went into the swamps of Lernea. Athene helped Heracles find the monster's home. Hydra and Heracles fought, but each time a head was cut off, another head grew in its place. Then Cancer, the crab, came out and bit Heracles in the foot. Heracles killed the crab and then killed Hydra by slicing off Hydra's immortal head. Heracles dipped his sword into Hydra's body. One wound from the sword would bring death to an enemy. The crab was given a home in the heavens for sacrificing its head.