Is purity useful?
It is very useful.
Gold of high purity indeed possesses the power of "purification," and the higher the purity, the stronger its purification ability becomes.
Just as high-purity gold ground into powder and mixed into gold paint made from palm oil and fine medicine can be used to dispel impurities—should the purity of gold reach a certain threshold, it can indeed be used to reduce the erosion of the soul.
Even Mr. Radiance has a special ritual for using gold to eliminate erosion.
It is a high-tier ritual in the field of "purification."
—In principle, this approach can certainly work. If there were almighty and invincible pure gold, then in theory, it could be traded for a purification power even purer than that of Mr. Radiance.
But that is only "in theory."
The problem lies in how to obtain such a fantastical thing?
"Gold with a purity exceeding one hundred percent... How could such a thing exist?"
