This unknown Tier 4 herbal grass was called Dodder Green Grass.
This kind of Quasi-Tier 4 medicinal herb was naturally not some rare object. But it was a rare thing in the Endless World.
In some medicinal theory records including the Herbal Compendium, there were simply no records regarding the Dodder Green Grass. Those so-called high-rank alchemists not recognizing it was also normal.
The reason why Ye Yuan took a fancy on this Dodder Green Grass was that this was one of the core ingredients for a Quasi-Tier 4 medicinal pill, the Purple Heart Soul Luring Pill.
This Purple Heart Soul Luring Pill was precisely the upgraded version of the Soul Luring Pill. It was used to break through to the Soul Sea Realm.
Except, this Purple Heart Soul Luring Pill's medicinal effects was on an entirely different level from the Soul Luring Pill.