The Thing, a 1982 sci-fi horror film about an Antarctic underground facility, has been combined with a Dwarf Fortress mod called The Parasyte-Thing.
As you may have guessed from the title, the mod is inspired by The Thing and Parasyte, a horror manga series that also features tiny alien organisms entering and taking over humans' bodies with horrifying consequences. Combine Dwarf Fortress's threats of necromancers, vampires, and werebeasts into one unpredictable, deadly enemy.
Parasyte things will appear at random when you have the mod enabled – modder GhostPutty claims they show up the way titans do, but they are most often the result of bites from infected animals in frozen biomes or the third cavern layer.
When that happens, you'll have problems – this is also known in the Dwarf Fortress community as 'FUN,' which is always capitalized. There are lumbering beasts with teeth growing places where they shouldn't be, dwarves splitting open to reveal toothy alien maws, and plant-like structures (also with teeth).
GhostPutty claims there are certain methods to either stop the spread of the beast or perhaps attract them — players may do both.
Parasyte-Thing is available on the Steam Workshop for Dwarf Fortress, and to get started, simply click the green subscribe button. Start up Dwarf Fortress and enable the Parasyte-Thing mod during world generation, and you'll be ready to embark on what's likely to be a very violent expedition.
If you like being scared or grossed out at your desk, check out our picks for the best horror games on PC.