Everypony hears stories about the forest. How it's "haunted" or "cursed" or filled with terrifying animals. How nopony who goes in ever comes out. Of course, these stories are all nonsense meant to amuse tourists. The forest most certainly isn't haunted or cursed or filled with terrifying animals.
There is something far worse.
Note: My first real attempt at writing something for Halloween. A lot darker than most of my other fan fiction, but I've long been a fan of horror and I wanted to write something that would fit well into the genre of "pony horror". Read at your own risk.