Lernaean Hydra
The second of the 12 labors of Hercules was to kill the Hydra. The monster also had one immortal head that was in the middle. All of the heads could spit deadly acid. To defeat the Hydra, Hercules called on his nephew Iolaus for help. As soon as Hercules cut off one head, Iolaus would cauterise the wound with a flaming torch so that nothing could grow to replace it. After removing the Hydra's immortal head, Hercules buried it under a large rock. Then he collected the monster's poisonous blood. In later adventures, he dipped his arrows in the blood to kill other monsters.