User with this ability either is or can transform into an Oni, variously translated as demons, devils, ogres or trolls. Depictions of oni vary widely but usually portray them as hideous, gigantic ogre-like creatures with sharp claws, wild hair, and 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 and are often depicted wearing tiger-skin loincloths and carrying iron clubs.