"That is a river of Qi. A river of pure yin Qi," Ensis said somberly.
"Yin Qi?!" Hao Xuan repeated, shocked.
In nature, Yin and Yang existed opposite to one another. Yin was of the cold attribute (generally) while Yang was hot. Yin was negative, and Yang was positive. Yin was black, and Yang was white.
Under normal circumstances, one element couldn't exist without the other. They were both two sides of the same coin.
Their duality was considered to be the balancing force of the universe. Without good, there was no evil. And without evil, there was no good.
Yin could not exist without Yang in nature. And an entire river of Yin Qi like this was certainly not possible.
But the most important part was that Yin was the dark element. Creatures that lived in the darkness and survived off of negative emotions were of Yin element.
"The cold, this is where it's coming from?" Hao Xuan finally realized.