User blog comment:Zathronas/Analysis by an author: Part 2 Antagonist, the Darkness/@comment-7387716-20131217141311

Unless hinted otherwise, there is a possibility that a more intelligent lifeform (more like a Grimm evolution) would pose a larger threat besides the Grimm by itself. All we know about the Grimm (from Mr. Port's class no less) is that they are dark monsters that look like animals. Not sure if there are human Grimm but as I said before, IMO the idea's not too far fetched as I initially believed.