Tesso, or the Iron Rat, is a demon in Japanese mythology said to be the size of a full grown man with metal teeth and claws that could shred almost anything. This demon also had the ability to summon swarms of regular rats to do its bidding. Tesso was originally a Buddhist monk named Raigo, however, due to being slighted in life he enacted a hunger strike which led to his death. Afterward, the anger he felt transformed his spirit into the demon.