Never noticed that before.
1 Eldritch Abomination stalking people for uncertain reasons.
1 Intrepid Investigator who is determined to find out the truth, at all costs.
And 1 Unknown Quantity who leaves Cryptic Clues that both Beguile and Frighten the Investigator.
The answer is, surprisingly, not a Slenderman Story but something a little bit older, and based on the West Virginian version of Bigfoot. I’ma go watch it now.