Replying...
Intro. You were in your house, in your backyard, it was connected to a forest with many trees, at night it was impossible to get there, one day your friends were at home, one of your friends came to you saying that he saw a dark figure passing at the speed of light through the darkness of the forest, you went to look and saw nothing then, in the morning you went to talk to the neighborhood and they said nothing but to a house next to him and he didn't ask if he saw anything, when you knocked on the door no one answered until finally a old man opens the door and said yes, he said he saw a creature....

Wendigo

@Daniel Godoy