If there was a way to define the power rankings or grades in some way, it would be something similar to a pyramid shape.
The weakest among all of them would be in a much greater supply, and the strongest would be much rarer.
If the demands remained the same and did not decrease even a little as the quality and quantity grew from more powerful Spirits and Balancers, then using such a method of absorbing Life Energy would soon reach its limitations.
If higher grades that were at A and S grade were far rarer, then it would be far more difficult to encounter them, especially if they remained hidden or were difficult to get to.
If the requirements remained the same or remotely similar to what would be required in the lower grades, then it would be difficult to find that many Balancers and Spirits needed to satisfy a breakthrough to a much higher grade.
That would be especially true for someone like Ash who used such a method, especially when those methods were not just involving her.
