Ongyo-Ki

This is my vision of Ongyo-Ki, one of the four onis with special powers that the wizard Fujiwara no Chikata, according to legend, invoked to take control of Japan during the Heian era (794-1185). His name could be translated as "the Stealth Demon", and he had the power to conceal even his aura, becoming undetectable, before attacking his enemies. Like his three teammates, he was "repeled" when a poet called Kinotomoo uttered these words: "All things, be it grass or trees, are ruled by the Emperor, and not even a demon can stand back to the Emperor and live on these lands". The four onis were "blown away", Chikata was arrested, beheaded, and his head was thrown into a river...
The "canon" information is limited to this, but it is also said that this Oni's powers would have inspired ninjutsu ; this art having been used for the first time during the Genpei war (1180-1185) according to the Shôninki (which could be translated as "The Authentic ninja chronicle"), it is not impossible, although the information should be treated cautiously. But his defeat is... rather disappointing. I mean, the onis have had their own "Fantastic Four", we could have expected a bit more !