User blog comment:Zolnir/RWBY Episode 6 Review/@comment-13616152-20130823142330/@comment-10390252-20130823151708

Flesh and blood (assuming that is what the Creatures of Grim are made of and Pyrrha's exposition makes that iffy) isn't as resistant to a razor-sharp blade travelling even at normal human warriors speed and strength as wood is.

At the moment, I'm resisting a Clarke-tech explanation where Crescent Rose's blade is made out of some kind of super-hard alloy with a molecule-wide cutting edge able to penetrate nearly anything.