The Immortal Forbidden Land in the depths of the Prison Department was originally one of the main palaces of the Ancient Sovereign Mystic Nether which were spread over the Wanggu Continent. In the past, every place was a holy palace.
Only the imperial family could stay there.
There was only this one place in the entire Holy Wave Large Region.
However, with the arrival of the god's fragmented-face and the departure of the Ancient Sovereign Mystic Nether, that place had been occupied by the fishbone god. Hence, the Imperial Immortal Palace became Immortal Forbidden.
The many treasures inside were also corroded by the anomalous substances.
It was very difficult for mortals and even cultivators to step into it. Even the Human Sovereign of the Eastern Triumph era wasn't willing to start a war with the god for this immortal palace.
