User blog comment:Berserkchart486/Warring States Fanon Canon/@comment-6673974-20141225023253/@comment-6003865-20141225044058

Based on how I think of it, any technique of any rarity, most likely is extinct. You'd have to reinvent, or by some miracle collect a scroll that contains details of the technique, though since most of those techniques probably didn't warrant a legend about them, likely there'd be no knowledge they existed at all.