And for Fang Hong to use the Mirroring Command, he also needs the basic theory of Flexible Construct along with a series of advanced theories.
Thus, the Knowledge Skills in Eteliria, especially those basic theoretical Knowledge Skills, often represent the starting point for a series of skills.
Of course, the Thief's Claw Technique he learned is so basic that it doesn't require any profound theory. But once it involves advanced skills, he still has to go back to fill in the gaps—Nightingale Basic Tactics was born from this. Related to this are the Shadow Realm, the Shadow Web Theory, and a series of Nightingale knowledge that are related yet branched in different directions.
