12) Korea - 6. Geuseundae

Its name is presumed to be derived from words like 'geuneul' (shadow) and 'geumeum' (new moon), interpreted as 'a large being standing in the darkness.' There are theories that it was a guardian deity during the Goryeo Dynasty but became an evil spirit during the Joseon Dynasty, or that it is a deification of darkness. It usually appears as a child but can freely change its size, and its power grows stronger with deeper darkness. It can startle or kill people with its large body, either by swallowing them whole or by causing those who pass under its legs to fall ill and die. It is weak to light and flees when threatened with torches. If surrounded by multiple people holding torches, it disappears, but it cannot be killed by physical means. According to a related legend, during the Joseon Dynasty, a warrior named Unmongseon tried to kill Geuseundae with his sword, but instead of dying, its body only grew larger. Geuseundae then caught and threw Unmongseon, killing him. It likes crayfish, and it is said that it will not harm those who offer them. Because of this, there's a theory that it's a yokai created to prevent children from going missing while catching crayfish, while simultaneously instilling a fear of the night road.