Wendigo is described as malevolent monster that possesses human beings, causing aggressive behavior, increased  and irrepressible  hunger, and eventually waking up cannibalistic and murderous instincts.

Here is the authentically terrifying, true-life story recounted by historian Robert Damon Schneck in a chapter of his classic underground collection of weird Americana, which formed the basis for the major motion picture, The Bye Bye Man.