The Lernaean Hydra was born to Typhon and Echidna. While not the most powerful of its siblings, the Hydra was a fearsome and vicious monsters with nine heads (at birth). The monster terrorized the Kingdom of Lernea, chasing all of the inhabitants away with the toxic acid and fumes that it spewed at them. When one of the Hydra's heads was decapitated, two more snake-heads would grow in its place.
The Second Labor of Hercules
As the second of his Twelve labors, Hercules was tasked by King Eurystheus to murder the Lernaean Hydra. The hero eventually defeated the monster by having his nephew Iolaus cauterize each stump after he had cut it, then tearing off the immortal head with his bare hands and crushing it under a giant rock. After defeating the monster, Hercules dipped the tips of his arrows in the Hydra's bile, rendering the weapons extremely venomous.