Oni are powerful, ogre-like demons from Japanese folklore, often depicted as large and fearsome with horns, tusks, and bright skin colors. They can be malevolent beings that cause misfortune, serve as enforcers in Buddhist hell, or appear as guardians of the underworld. While often associated with destruction and terror, the image of the oni can vary, with some tales portraying them as symbols of good luck or even as complex characters in modern media.