Onis are large Ogre-like demons from Japanese folklore. They are popular characters in Japanese art, literature and theater.
Depictions of oni vary widely but usually portray them as hideous, gigantic ogre-like creatures with sharp claws, wild hair, and two long horns growing from their heads. They are humanoid for the most part, but occasionally, they are shown with unnatural features such as odd numbers of eyes or extra fingers and toes. Their skin may be any number of colors, but red and blue are particularly common. They are often depicted wearing tiger-skin loincloths and carrying iron clubs, called kanabō.
Oni are stated to be representatives of ill-fortune, bringers of disease and disaster that supposedly devour humans. In fact, they were originally conceived as being invisible spirits without a tangible form, only taking on their ogre-like appearance with the introduction of Buddhism to Japan and synchronizing with other mythological beings such as gaki, rakshasa and genies.