The Celestial Conflict
In 0AW a battle took place between the Avatar of Hell and the Avatar of Earth against the Avatar of Heaven. The Avatar of Heaven had effectively neutralized the combat potential of all the ninja villages by eradicating their armies with a special mass destruction ninjutsu. The Avatar of Heaven fought the Avatars of Earth and Hell for two straight days until he was eventually defeated and sealed away. This is the officially marked end of the 30 year war.
The Avatar of Heaven’s body was given to the now neutral nation created out of the remnants of thier battlefield (The Shattered Sky Nation). Until just recentsly (7AW) he remained sealed until he was released with very special seals to attempt to rehabilitate him and use him as a bargining chip in the upcoming war.