The legacy left behind by Sacred Ancestor High Priest let Ye Yuan have a clear understanding of Alchemy Dao realms.
Before the Dao Realm was the Initial Realm, surface level, ignorant about Dao; getting to know the Alchemy Dao was the Initial Realm.
Initial Realm alchemists relied entirely on experience when refining pills and could not find the proper approach. Hence, it was very hard to refine high-quality medicinal pills.
After Initial Realm was Dao Realm. Dao Realm alchemists already understood the Great Dao. Refining pills were accomplished with high proficiency, refining divine-grade divine pills were also accomplished with high proficiency.
Ye Yuan entered this realm since he triggered Great Dao Heavenly Melody.