User blog comment:Zathronas/Analysis by an author: World of Remnant, Grimm/@comment-32598036-20141017125043/@comment-24218038-20141017130030

That's a very good question, Hmmm how about a rock-like creature, Insect maybe or Man itself.

A long time ago, I speculated that a Grimm with human aspect could show up later in the series. Maybe even with the ability and intelligence to lead the other Grimms. My idea behind it was that the underpowered Grimm we knew then would become a greater threat that way.

Maybe I had something there.