Hell on Earth - Horror Mod is a mod for Fallout: New Vegas which premise could be described as Fallout: New Vegas meets Silent Hill. It includes an optional plugin which adds the Otherworld/Nightmare Realm, a horrific version of some areas of the Vanilla game.
- After the End: ... Except it's an apocalypse triggered by a scientific experiment instead of a nuclear war.
- Crapsack World: It's a post-apocalyptic world merging with its dark world, full of monsters, and various thugs.
- Cult: An optional plugin turns the Legion into dangerous frightening cultists from the Otherworld, by changing their outfits.
- Dark World: The Otherworld/Nightmare Realm, which is entered and left through one way portals. The places having an Otherworld entrance are Novac, Camp Searchlight, and The Strip.
- Genre Shift: Turns the game into a Survival Horror.
- Hell Is That Noise: Youre hinted youre getting near an Otherworld entrance when you start hearing a siren sound.
- Ominous Fog: According to the mods backstory, one appeared after the experiment which opened the Otherworld. In proper game, such a fog only appears if you install the optional mod Nevada Skies
- Survival Horror: Not only it has the atmosphere and scenario of one, but it also contains optional plugins which make the interiors darker and reduce the amount of ammunitions you can find.
- What If?: In the mods backstory, the nuclear war of 2077 has been replaced by a disaster in which experiments about interdimensional travels caused the discovery of a Dark World which slowly merged with our own dimension.