As cool as a mind/dark mind-flayer type critter would be, Hasbro owns the copyright and they have nazgul for lawyers.
Though it would be a cool opportunity to make our own squamous brain vampire horror.
What sorts of animals do people find disturbing?
Wasps, especially the kind that leave you paralyzed while their offspring grow fat within your slowly liquifying organs?
Swarms of Millipedes? But with even extra-more legs? That live in the fluid of their victim's eye, until they grow too large and burst forth?
Catfish with barbed hypnotic whiskers that attach like lampreys to the base of the victim's skull, pulling the victim's spinal cord like a puppet?
Ideas?