Choosing what flames to use for pill refinement was also a type of skill.
Right now, An Lin had six flames to choose from—Demonic Star Flame, Great Holy Flame, Setting Moon Flame, Heavenly Void Flame, Mutant Blood Phoenix Flame, and Holy Vermilion Bird Flame. If he included the Golden Dragon Flame from the Divine Flame Bead, then he had seven flames to choose from.
The choice of flames would depend on what pill one wanted to refine.
The more control one had over their flames, the lower the chance of making mistakes during pill refinement. Moreover, a high-quality flame could improve the essence of a pill, giving it more spirituality and divinity. The overall rank and quality of the pill would also be given a boost.
An Lin was refining a ninth-rank spirit pill; what would he care about quality? He would thank the heavens if he didn't make any mistakes. Thus, he was naturally going to pick the flame that he was most familiar with.