Thirteen
The Impurities of a substance weren't as simple as they seemed. It could be said that the way Impurities were different depending on what the origin of them was.
Impurities, as Ryu had said, were far more complex than he had ever given them credit for. They were often the byproduct of the world creating, and could be said to be an act of balancing by the Heavens.
After the Natural Treasures were cleansed, Ryu was even able to notice that the gap they had closed down was actually related to the level of the world itself!
This sounded confusing, but simply put, the weaker the world, the more impurities there would be in creating the same treasures. That was why without these Impurities, the Natural Treasures that Ryu made use of were made to be even more powerful!
So why was this important now?