The terror of the Evil Spirit, Li Yan and his team were acutely aware of.
This thing is considered a rare "Sha," only born under extreme circumstances, and incredibly troublesome to deal with.
Outside of Chang'an City in Guodu Town, due to a Bloodline Curse, it transformed into a demonic bird Rashamon, appearing and disappearing without a trace; those attacked by it suffered extremely gruesome deaths...
On Hua Mountain, the "Sha" transformed into the Feiyi, not only devouring spirit wood but also absorbing the Drought Demon Qi...
Li Yan had later specifically researched this.
The "Sha" comes in five colors: blue, red, yellow, white, and black, corresponding to the Five Elements.
The type that gave birth to the Feiyi is "blue Sha," which can destroy spirit wood; regardless of the type, they are extraordinarily vexing.
Xie Chengzu's ritual was essentially a negotiation.