Forty thousand years ago.
In the Netherworld, the Eighteen Levels of Hell.
One day, without any warning, Jie, the foster son of the Ancestor of the Nether King who had been appointed to oversee Hell, unilaterally unsealed the Gate of the Nether King, releasing three Primordial Demons of the Underworld.
After escaping from the Gate of the Nether King, they directly destroyed the eighteenth level of Hell, and all the evil spirits imprisoned within were set free.
Not long after, the Ancestor of the Nether King led the Clan Leaders of the Eight Great Clans, along with the Niu Tou and Ma Mian army, to subdue two of the Primordial Demons and re-seal them within the Gate of the Nether King, while the whereabouts of the third Primordial Demon remained unknown.