By skyforbes 
The horror of the unknown can really elevate a creature too incredible levels and I love whenever a piece of media prevents you from being able to get a clear image of its entity during its entire runtime.
The tunnel stalker – The tunnel(2011)
Only seen in quick glimpses the Stalker is most clearly seen in the image provided, it can be recognized as something humanoid but all the specifics of its full body and even its origins are never explained
The cave inhabitant – Ted's caving journal by Alex Archives
The inhabitant that Ted encounters is never shown or explained in the series, the only things we know about it are all depicted from audio or how it interacts with other things, like how it screams when the characters are drilling into the cave or how it pulls the rope of one of the characters.