Four small figures darted to and fro amidst the medicinal items that were emitting fragrances in the enclosed medicine refinement lab, being very busy.
"Obtain three Stellar Grass!"
"Pluck two Unwithered Silver Flower!"
"Little Tea, pluck a blade of tea leaf off your head and give it to me!"
...
Feng Lin sat before the furnace and kept on forming seals with his hands, controlling the true fire.
The quartet listened to his orders and docilely treated the many spiritual herbs accurately, tossing them into the furnace and tempering them into pills.
They were plants that had turned into demonic spirits and were very sensitive toward medicinal properties. Thus, they could accurately grasp the characteristics of medicinal herbs. It was a talent they were born with.