Forbidden City Sweeper

I worked in the Forbidden City repairing cultural relics for fifty years. After my death, I became a handyman in a fantasy world. There are swordsmen and demons everywhere here. They laughed at me as a mortal, worthy only of sweeping the floor. Until one day, the sect-protecting formation was breached by the demons, and disaster struck. I silently picked up the broom and drew a line against the demonic clouds in the sky. ——This line can be crossed by humans, but not by demons.