User blog comment:Da1337wolf/Speculating Aura and Dust/@comment-23784953-20130824233222

Eh, variants of Ki which can't be used by certain creatures exist in anime. Aura is just a variant that can't be used by the Grimm. In the universal scale of things, it acts the same as what we've seen in other anime.

I think you're jumping the gun with calling the Grimm "undead". Not every being without a soul can be classified as dead. They're monsters, yes. But not zombies.

One of my theory is that the Grimm are formed as a counterbalance to Dust AND Aura. Planet RWBY has this harmony thing going on and these two factors are duking it out.

I find your speculation that the Grimm can use Dust odd. It requires a bit of knowledge to utilize Dust. (and in Ruby's case, a sneeze) Sure, they may use it accidentally, but not deliberately. Maybe a smarter Grimm may do so, but not a Beowolf or anything on par.

Well, at least I'm not the only one who considers Blake's bow impossible to hide any ears. Plus it would be silly to make her have four ears....... yet Rin Kaenbyu did it so I'm not saying it's entirely impossible. So I'd say there's a chance this is true by 20%.

Overall, you provide some decent theories. I find it possible that at least one of them will become real.