How Was the Demon King's Castle Built?

The universe is filled with boundless darkness and chaos, and somewhere in a dark corner, an extremely disharmonious scene appears. The already barren land was fenced off for construction. It looks like a construction site. No one knows what is happening in this "construction site". You can only hear the mechanical roars and low roars coming from a distance. "You're slacking off again! Go to work!" This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.