Here is my illustration of an Oni. Oni are a kind of supernatural ogre like creature in Japanese folklore. Oni are typically portrayed as hulking figures with horns growing out of their foreheads.
I took the inspiration for the face of the Oni from a photo I took at a traveling exhibit of samurai armor. The armor is from the Ann & Gabriel Barbier-Mueller Museum, in Dallas, Texas. I thought the face mask had a very Oni look.