Jack Horne is someone that utterly terrifies the monsters.
For the moment, he is as human as they come, but the smell of death surrounds him. The monsters know that this means he has been marked, and that the spirits of three hundred angry dead is a heavy burden for a human to bear. That a human carrying that many angry dead souls with him does not have a happy ending.
That a human with so much blood on his hands becomes an eater of monsters upon death.
Humans think wendigo only eat human flesh. Monsters know that they, too, are on the menu. And the four traveling with this group do not intend to be supper.