The Dai-Oni present at the Tourney of the Planes, despite being a Demon of not inconsiderable power, is bound by powerful laws of etiquette - though not necessarily unswerving politeness, as demonstrated by it insulting the Ki-Rin - such as allowing a hero to ask of it one thing if the Dai-Oni is defeated, which the Dai-Oni has to answer. It was stripped of its magical powers by the Ki-Rin and then slain in combat by the Samurai Kensei, revealing to him the secret of the Dai-Katana before he was transported to the realm of Ikiru.
The Oni are a class of magical creatures varying from the size of a small child to that of an 8 foot giant (Dai-Oni). The Oni are evil spirits or Demons that have monstrous forms. There are many kinds of Oni, but the most recognised are the Oni of hell. These creatures can be green or red and have either the head of an Ox or a Horse, with a Human body and are often depicted with horns and wearing Tiger skins. They capture sinners and carry them in a flaming chariot to the god of the dead. Oni have the ability to change their shape but all are said to be malevolent and the cause of disease. Some have suggested that rather than being a Demon an Oni is more attuned to an evil Genie or Djinn.
- In Japanese, "dai-oni" means "great demon".