Lethifold

The Lethifold (also known as a Living Shroud) is a carnivorous and highly dangerous magical creature. It is also considered a Dark creature because of its aggressive and violent nature.

Physical description
"It resembled nothing so much as a rippling black cape, the edges fluttering slightly as it slithered up the bed towards me."

- Flavius Belby's account of a Lethifold attack

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, by suffocating and digesting it.

Protection from a Lethifold
The only form of protection against a Lethifold is a Patronus, similar to a Dementor. Other spells such as the Stunning Spell will not work.

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

Lethifold attacks
The first recorded survivor of a Lethifold attack was a wizard named Flavius Belby. Belby was on holiday in Papua New Guinea, and he managed to escape because he was not fully asleep at the time. He repelled the Lethifold with a Patronus Charm, something other victims have been 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 to their presence.

Much easier to calculate is how many people have faked a Lethifold attack, for their own reasons. 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.

Celestina Warbeck's parents met when the man who would become her father saved his future wife from a Lethifold that had disguised itself as a stage curtain during one of her performances.

Etymology
"Lethifold" comes from two roots: lethum, variation of letum, which is Latin for "death", "annihilation", "ruin", and fold, which possibly pertains to the creature's cloak-like appearance. Lethi- is also similar to Levi-, which is reminiscent of levitation (an ability of the Lethifold) and levis, a Latin adjective, meaning "light" (a quality that Lethifold also possess). It can also be related to "lethal", which means "causing death". It is possible that the Ancient Greek lethe, the name of one of the rivers of Hades and meaning "forgetfulness", is also a point of origin, since mortals touched by its waters forgot their lives, ceased to struggle, and (generally) drowned.

Behind the scenes

 * It is possible that the Lethifold could be a hybrid or a relative of the Dementor, for their similar descriptions, inhumane behaviours, and vulnerability to the Patronus Charm. However, Lethifolds have been classified as beasts, whilst Dementors are non-beings.
 * According to W.O.M.B.A.T., Dementors may be unknown in tropical regions, while Lethifold are found only in tropics.

Notes and references
Moremplis Kalmolaskos Lethifold Смеркут Śmierciotula