Yugen- sometimes also called Golden Chi- is a special, but weaker form of Chi that is used by the Shinma. Because they are unable to reach the Spirit Realms, the Hsien are forced to collect and gather Chi in order to survive. Yugen is undifferentiated (not Yin or Yang) Chi produced by the interaction of a hsien’s Chi with the Chi from the Yin and Yang worlds. This is only gathered at Dragon Nests and during religious festivals -- basically, places and times when the Wall is weak.