It's attributed various powers, including flight, invisibility, the projection of illusions, and a keen tracking sense for its prey - typically unwary travellers, especially young and foolhardy ones.
The most common origin for a Wendigo is the consumption of human flesh during a harsh winter; this awakens a feral hunger that gradually transforms one into the monster. Intentional association with fell powers ('bad medicine') can also achieve the same result.
The Wendigo has been made most famous by its use by Algernon Blackwood in his short story The Wendigo. It's since inspired a Marvel comics character by the same name and various movies and television shows.
Also a well-known knave from Gaia Online.
"A Wendigo? What do you mean?"
"Pray you never find out, son."