Outside the Nantian Gate, deep in the Heavenly Prison, half of the evil spirits in the Three Realms are suppressed. There are the remnant souls of ancient demon gods, unruly immortal generals, defected demons, and even the remnants of the monkey genus who were captured when they wreaked havoc in the Heavenly Palace. Jiang Cheng, a prison officer whose identity is a mystery, holds the "Prison Order" and has been guarding the deepest part of this prison for three hundred years. He does not see the sun, but he has insight into the situation in the three realms; he is not involved in the disputes between immortals and Buddhas, but he is closely connected with every great catastrophe.
When Sun Wukong made a big fuss in the Heavenly Palace and was pressed into the Five Elements Mountain, the Heavenly Prison ushered in a brief period of peace. However, Jiang Cheng smelled something unusual from the prisoners' words - this was not a simple "punishment", but more like the beginning of a carefully planned event. After that, the road to learn scriptures opened, and along the way the demons either escaped from the Tianlao, or had deep connections with the prisoners in the Tianlao. Whenever there are changes in the three realms, cracks will appear in the heavenly prison, and the evil is ready to move. Jiang Cheng has to hold the prison order and step into dangerous places again and again: going to the underworld to pursue fugitives, entering the Flame Mountain to suppress the remnant soul of the ancient fire demon, breaking into the Lion Camel Ridge to check the roster of the demon world, and even facing the "source of crime" hidden at the foot of Lingshan Mountain.
His prison-suppressing order can command the dark soldiers of the heavenly prison, can uncover the false truth, and even hides secrets that he himself has never known. As the team progressed, Jiang Cheng gradually discovered that his existence was not only to guard Tianlao, but also the key to the balance of yin and yang in the three realms. Some of the suppressed prisoners were his "old acquaintances" and some were "foreshadowings" of his fate, and his identity was actually closely related to the reshaping of the Three Realms. On the day when the sutra study was successful, the Buddha's light shone in Lingshan, but Tianlao faced the greatest crisis. Jiang Cheng finally understood: Keeping the prison is never the goal, breaking the situation is destiny.
