Lethifold

The Lethifold (also known as a Living Shroud) is a carnivorous and highly dangerous magical creature, and very similar to a Dementor. Its appearance resembles that of a black cloak roughly half an inch thick, although it gets thicker if the Lethifold has recently digested a victim. It glides along the ground and other surfaces in an unknown form of locomotion in search of its prey, humans. It attacks its prey at night, when the target is asleep, and suffocates and digests it in its bed.

The Lethifold is a very rare species, and can only be found in the tropics.

Lethifold Attacks
There has been only one known survivor of a Lethifold attack: a wizard named Flavius Belby. Belby was on vacation in Papua New Guinea, and she managed to escape because she was not fully asleep at the time. She repelled the Lethifold with a Patronus Charm, something other people are unable to do because they are either asleep or Muggles (or both). It is impossible to determine the number of Lethifold victims, as they leave no clues of their presence.

One known case of an individual attempting to fake a Lethifold attack was Janus Thickey, who disappeared in 1973, leaving behind a note reading "Oh no, a Lethifold's got me, I'm suffocating". Because of this and his empty bed, Thickey's wife and children began mourning him. However, he was soon discovered living five miles away with the landlady of the Green Dragon.

Etymology
Lethifold comes from two roots: "lethum", variation of letum, which is Latin for death, and "fold", which possibly pertains to the creature's cloak-like appearance.