For the Aurous Core Stage cultivators in the Intermediate Stage to promote to the Advanced Stage, they had to overcome the Tribulations of the Yin Wind.
The spiritual energy that a cultivator consolidated to overcome the tribulations converted to Yin Wind. It would then blow up from the "Baihui" acupuncture point at the top of his head. In an instant, his soul would leave his body. It could not be stopped and the soul would sink-float in space.
The Tribulations of the Yin Fire was used to remove impurities from the Aurous Core. Whereas the Tribulations of the Yin Wind was to make the Aurous Core surface flawless.
After going through these two obstacles, the Aurous Core of the cultivator would become perfect. This was also a preparation for the formation of the Nascent Soul.
Zhu Yi began challenging the Tribulations of the Yin Wind and pushed for the Advanced Stage of the Aurous Core Stage.
