This list of mythical creatures that begin with this letter and I am constantly gathering information from each continent, and is continually being updated.
Nukekubi (Japanese)
The nukekubi are rokurokubi whose heads come off and float about. These were the last of the rokurokubi whereas the other kind came before. Nukekubi sometimes perform bad deeds such as attacking at night and drinking their victims' blood. It is theorized that the nukekubi has a weakness when it is sleeping and the head is floating around: If the body moves, then the head cannot be re-united to the body.
Like the rokurokubi, being a nukekubi is considered a curse. Edo period scientists believed that nukekubi suffered from an infliction similar to somnambulism; only instead of walking about at night the patient’s entire soul and head depart from the body. Uncured, this curse has the potential to tear a family apart, particularly due to its violent nature.