Darkness has descended on the earth, and eternal night has enveloped the world. Only the Great Wall of China maintains the alternation of day and night. Along with the darkness came countless demons and ghosts. The Great Wall blocked the eternal night, and powerful demons could not cross the Great Wall. But whenever day and night alternate and night comes, low-level demons can still cross the Great Wall and threaten the territory of China.
The protagonist Chen Yang accidentally survived the nuclear explosion, and a mysterious palace was added to his sea of consciousness. He repaired the palace, awakened the emperor, and went through the palace step by step to trace the source of the eternal night.
A pretty good book