Pilgrim is a mod for Fallout 4 that takes Bethesda's Commonwealth and turns it into something you'd see in a game like Silent Hill.
It doesn't add new much new content, so there won't suddenly be quests to chase down chainsaw-wielding hick families or bog witches. But what it does do is overhaul the game's weather, sounds and environment lighting to create a "dreadful atmosphere" for wandering around the woods like someone who's begging to get eaten.
In addition to all that there's a dynamic music system in place now as well, which changes based on the weather and which features an all-new soundtrack that's more appropriate for the visuals.
There are a few download you'll need if you want to try it out; you can grab them all here.