Outside Celestial City, the sky was as red as blood and as dark as ink, with no light from the sun or moon, and jagged rocks everywhere.

In the eternal night that even a thousand years of rain couldn't wash away, there were occasional inhuman wails and whispers that sent chills down one's spine.

A grand and wild Great Wall stood as the dividing line between the human world and hell.

The history passed down by word of mouth in the Three Cities of Heaven, Earth, and Man tells that the outside world is a forbidden zone for humans, and within Celestial City are two worlds.