User blog comment:Da1337wolf/Speculating Aura and Dust/@comment-4773581-20130824223350/@comment-4773581-20130825003417

I disagree with the only way for the Grimm to have been born without souls is to be unnatural, and I disagree with those being the only possibilities.

The Dust theory is a bit out there, but otherwise not too bad.

The Fauna/Faunus/Fauni/Phones theory is pretty standard.