Those below the Heavenly Immortal realm who can fly are eligible to enlist for the battle, meaning one's cultivation must reach the Human Immortal realm.
In reality, it's hard to find any prisoners of the Heavenly Immortal realm in any prison. Those who reach the Heavenly Immortal realm and are imprisoned but not killed are the mainstays of various powers. Even if they're Loose Cultivators, it's not easy to get them inside in the first place.
Participants will be thrown into the territory contested by five factions. As long as one can win, any despicable means can be used, and any magical treasure can be brought in, even poisoning is permissible.
From this, it can be seen how brutal and bloody this 'Battle of Great Pardon' is.
Essentially, every hundred years, it's held once for these disputed territories. This is the origin of the 'Centennial Great Pardon.'
