To me Cthulhu wise my first thought is they got a Flying Polyp vibe to them.Fell Taints really remind me of some monsters from a Cthulhu Now scenario called "Fractal Gods." Does anyone who is familiar with that scenario get the same vibe, or is it just me?
They all attack NADS rather than AC, which will hurt the heavy armour types a lot.
The other thing is that they're the first monster I've seen(*) that is actually rewarded for CdGing a PC.
(*) Though I certainly could have missed others, and I haven't got MM2 yet..