In Greek myth, the monster known for its multiple heads is the Hydra. This creature, originating from the Lernaean swamps, had the ability to regenerate multiple heads when one was cut off, making it a formidable adversary. The hero Heracles was tasked with slaying the Hydra as part of his Labors. Each time he cut off a head, two more would grow in its place, symbolizing the challenges heroes face in overcoming adversity.