A Shadow Person, also known as a Shadow Figure, Shadow Being or Black Mass, is an alleged paranormal entity. Paranormal researcher Heidi Hollis has expressed the belief that shadow people are malevolent supernatural entities.
A number of religions, legends, and belief systems describe shadowy spiritual beings or supernatural entities such as shades of the underworld, and various shadowy creatures have long been a staple of folklore and ghost stories.
Several physiological and psychological conditions can account for reported experiences of shadow people. These include sleep paralysis, illusions, or hallucinations brought on by physiological or psychological circumstances, drug use or side effects of medication, and the interaction of external agents on the human body. Another reason that could be behind the illusion is sleep deprivation, which may lead to hallucinations.