The Dark Crystal had creatures which looked like Bats, but had a splinter of a crystal instead of a big eye in their "head". This acted like kind of what we would call a camera, which showed the Skesis in their hall everything that bat alaso "saw".

So it was kind of a magical creature : Half life-form, half crystal. Not able to reporoduce, but able to show its "superiors" everything it "saw". I guess it had no real own "will" either.

When you find a big kettle of crazy, it's best not to stir it.
--Dilbert cartoon

"Interplay.some zombiefied unlife thing going on there" - skavenhorde at RPGWatch