Board Thread:Episode Discussion/@comment-24573226-20161003151422/@comment-10390252-20161003164532

GreyStark wrote: Anyone else wonder, Wtf is going on with the Grimms' eyes As the darkness grows deeper, the Grimm are becoming steadily more and more overtly demonic in their appearance - the glowing eyes, the fire that lies beneath their hides and the fact that they can now barely hold together their corporal shapes, thus the clouds of smoke around them. These are not natural life-forms; they may not even be life in a strict definition of the word but, rather, some kind of Dust byproduct, energised and animated by negative emotions.

The eyes just emphasise that they have more in common with a fire demon than any form of life.