After an incense stick of time, Nian Huan and Jia Baihe finally understood the reason.
A new method of advancing in the Great Dao appeared in the Fog Realm, which involves purifying one's own Taoist Rhythm.
Especially many Saints stuck at the fifth step of the Great Dao, at the level of Wuque Saint, or the sixth step, at the level of True Saint, all because their own Taoist Rhythm was too mottled.
Once potential is exhausted, they can only remain at a certain level without making any progress.
If they want to advance, they must remove the mottled Taoist Rhythm from their own Great Dao.
Peeling away their own mottled Taoist Rhythm is purifying the Taoist Rhythm.
Purifying mottled Taoist Rhythm is most commonly done by Slaying the Dao.
But Slaying the Dao is too dangerous; first, the Dao Slayer must have a firm will.
If the will is not firm, there's a very likely chance they'll cut off their own Primordial Spirit while Slaying the Dao.
