Grumfriel might be a scrambled word game. I found the word Glurm, witch as fart as I know means something similar to regrettable, as in something happened that is regrettable.
So you weren't sure about Grew, I think it might mean Grue, witch is a mythical beast. It's an ocular man bat. It's known for hunting prey in the dark. So maybe it's saying he's in the dark? Or he's left us in the dark.
