Well, isn't that just the stuff of nightmares. I'm guessing its... its... mouth feelers? Yeah, we're going with mouth feelers. My bet is that they provide the Fendahl with all the sensory stimuli that a tongue, nose, and possibly even eyes afford us.
Was there a reason they wanted a glowing skull? And when I say "they", I mean both the Fendahl and all other interested parties.