Imugi
Imugi (이무기) is the immature dragon of Korean folklore: a great hornless serpent that failed to achieve full dragonhood, sometimes because it lacked the dragon jewel or could not climb the storm-ladder to heaven, and must wait a thousand years. Tales vary on whether it is benevolent or ominous, and 'imugi' sightings are also folk explanations for lake and river serpents.