A Hat Man, a type of Shadow Person
Shadow People, also known as Shadow Figures, Shadow Beings or Black Masses, are supernatural and paranormal entities, often believed to be malevolent in nature; they are also often associated with feelings of tremendous dread. They are often considered either a type of ghost or demon, depending upon the individual's personal perception and opinion. They appear as dark silhouettes with fully- or partially-human shapes and profiles that flicker in and out of peripheral vision. Though some manifest as full figures, others have more nebulous attributes to them. The flickering may appear to move at an 'unrealistic' or 'hyper realistic' state.
Shadow People or similar beings have been described in numerous religions, legends and belief systems over the years, sometimes as shades of the underworld; various shadowy beings have been a staple of folklore and ghost stories for a long period of time. Besides the immediate feeling of terror or dread associated with witnessing one of these beings, other psychological and physiological conditions are also associated with their presence, including sleep paralysis, illusions or hallucinations. However, these are most often considered to be the underlying reasons for an individual seeing a shadow person, not vice versa.
Another similar creature is known as the Hat Man, which is essentially a Shadow Person wearing a hat.