In the first year of the Dark Yuan Era, a demon star fell on the shore of the North Sea, and the earth was slowly covered by the demonic energy in the demon star, and thousands of living beings withered, and the human race ushered in the darkest era. In order to survive for 3,000 years, the Terrans had to rely on the spiritual veins to build magic circles and build towering cities one after another to isolate the demonic qi and find a respite for the Terrans. However, with the passage of time, the spiritual veins were also eroded by demonic energy, and one city after another fell apart due to the damage of the spiritual veins, and the guardian array was broken. ...... In order to maintain the spiritual veins and slow down the erosion, the monks of the human race have refined one guardian circle after another on the spiritual veins, but even so, they still can't stop the erosion of the demonic energy, in this case, they need to often send people to the land surrounded by demonic qi to regularly maintain the magic circle and check the spiritual veins, even this has not prevented the cities from collapsing and falling into ruins.