As Lind had grown his elixir mastery, he had learned it all boiled down to control and purity. Control was basic to any cultivation technique, but purity was the war waged by all.
Purity produced better results and left few issues behind to clean up within the body, but when it came to elixirs, it meant an entirely different thing.
Essence was the beginning. The very purest shape of each ingredient was boiled down to its essence that only spiritual Qi carefully controlled could pull out of each ingredient. Herbs grew in the real world so aside from what they needed, they also absorbed toxins, and other impurities.
Alchemists did their best to keep a tight garden but it was impossible to eliminate them all entirely in the growth process. Concocting then refined the ingredients and the more impurity removed resulted in higher grade pills.
