I used to have the same nightmare from time to time as a kid. It was basically a "monster under the bed" type thing and I would sit in my bed, leaning over the edge. There would be long, thin arms covered in dirty black fur matted with blood reaching out from beneath my bed in a scooping motion at the air. Through thin patches of hair I could see corpse-pale skin and the claws on the four-fingered hands (no thumb) were curved and yellowed with age (like a sloth's). The arms never stopped moving. Eventually I noticed one of the "things" under my brother's bed (we used to share the same bedroom) and it was a vaguely human creature. It had very long arms (sort of like tree-dwelling apes), and its whole body was covered in the same matted black fur. Their faces had bulbous eyes that were ivory-colored and looked like the blind eyes of something that lives in a cave. They had nose holes but no raised facial features. The mouth was very wide and held in a constant grin, bearing teeth that looked like porcupine spines. It would sit in a fetal position under the bed, rolling back and forth and making a sound between giggling and choking.

Anyone have any idea what this creature is/was?