From the moment his artistic realm 'stepped into the Dao,' his Essence Soul gradually transformed every time he painted.
After reaching the Grotto-Heaven realm, one just required sufficient time for their Essence Soul to become a fifth-level Essence Soul. After becoming a fifth-level Essence Soul, the benefits of passive growth would be much lesser than before.
After reaching the Heaven Earth realm, a cultivator's Essence Soul would definitely become a sixth-level Essence Soul given enough time.
As for obtaining a seventh-level Essence Soul? One needed to undergo emotional upheavals! They needed to create their own cultivation techniques to trigger the Essence Soul's transformation! Either that or they could obtain special opportunities like Essence SOul cultivation techniques. In short, to countless living beings in the River of Spacetime, obtaining a seventh-level Essence Soul was their limit.
