Hydra of Lerna

In Greek Mythology, the Hydra was a serpentine lake monster, thats lair in the lake of Lerna in the Argolid, a place that was also an entrance to the Underworld in the myths. The Hydra was a offspring of Typhon and Echidna, it has poisonous breath and blood, possesed many heads, on later versions of the Hydra, every head had regeneration feature, for every head chopped off, the hydra would regrow two heads. Heracles with the help of Lolaus (and Athena in some versions), killed the monster, as part of his twelve labors, later Heracles would use arrows dipped in the Hydra poisonous blood to kill other foes. Goddess Hera (also told she raised the hydra) upset that Heracles had slain the monster, placed it in the vault of the sky as the constellation Hydra, she then turned the crab into the constellation Cancer.