Hibernating for Fifty Years, I Am Invincible in the Darkness

Traveling through time and becoming the bottom secret guard of the Southern Song Dynasty, the start is on hell difficulty? Don't be afraid, I have a Netherworld Immortal Palace. One day in the outside world and thirty years of hard training in the palace! If you practice Qi, I will become a master; if you become a master, I will become a heavenly being; when you become a land god, the grass on my grave will be several thousand feet high! Fifty years later, when strange demons came and the great masters were like ants, everyone was confused: "How did that old sweeper, the most cowardly old man from the Imperial City Division, kill a god with one sword?!" This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.