Darkness is common, but this was the first time Ning Cheng encountered the rules of true darkness. The darkness he usually saw was merely an extension of the five elements or some exotic attribute rules between heaven and earth. Such darkness could be perceived with his Divine Sense, completely incomparable to the actual rules of true darkness.
Even with the Huang Zhu, which gathered all the various origins of heaven and earth, Ning Cheng still only managed to derive eight elemental roots. However, among his eight derived elemental roots, the dark attribute was lacking.
