Ether Gathering Techniques.
These techniques were accepted by many as the first building block that allowed a Sage to wield the powerful strength that they currently do.
Though, if one were to be more specific, the Basic Ether Gathering Technique was what many accepted as the first building block.
That's because with enough time and experience on the path of a Sage, it would be more surprising for someone to continue sticking with the technique instead of optimizing the technique's ether gathering capabilities.
After all, the technique was so basic that even a Second-tier Sage-to-be could find faults in it that they could fix.
But of course, just like how there were many realms before one became a Grand Sage, there were also limits to how much a Sage could optimize the Basic Ether Gathering Technique before they could no longer optimize any further.
And thus, the grading system for Ether Gathering Techniques was born.
