Planet Earth Realm was a realm with harsh physical laws and even Sages would be rendered powerless here.
With the invasion of the Spiritual Realm in the form of the Spiritual King Comet, the introduction of spiritual energy in the realm slowly led to the existences of mutants and special techniques.
Therefore, the Elemental Spiritual Energy Cultivation Spell which Fang Yuan had created was more suited for the Spiritual Realm than for Planet Earth Realm. Therefore, it would require the supplement of spiritual droplets.
If not for the fact that Fang Yuan had absorbed a few spiritual energy nodes previously, he would not have been able to advance in his cultivation so quickly.
This was also the same for Long Lizi, Venerable Moonchaser and Farquhar.
Before the fourth occurrence, no one would be able to attain the 5th Tier. This was why all of them were being defeated by Ancestor Red Cloud so easily.