- The entire game, really, in no small part due to the gloomy, oppressive atmosphere. Throw in dead bodies all over the place, the silence of the entire game, and everything either actively trying to kill you or easily capable of doing so by accident, and the whole experience is pretty unnerving. Some of the level layout seems specifically designed to induce this; a mid-game factory section features a vine in the foreground that looks distinctively like a spider leg, for example.
- That spider. Oh, god, it's creepy and it chases you and you're just a kid with no powers or defenses and it will not STOP.
- The game also compels you, the player, to do several disturbing things in order to continue, such as waiting for a parasite-afflicted kid to stumble into a lake and drown so that you can use his body as a stepping stone, or the eventual fate of the Giant Spider: later in the game, the spider reappears dragging itself toward you with its only remaining leg which you are forced to rip off (you can see the muscles and everything) and roll the limbless body of the still-alive spider into a pit of spikes as a makeshift bridge so that you can progress. What makes it worse is that it still twitches after being pulled off. Witnessing such deeds would be bad enough, but having to perform them yourself is just twisted.
- One of the pieces of artwork for the special edition of the game (pictured in the page image) has the exact same background as the regular cover for the game. However, instead of showing the boy running towards the light, it shows the boy being lifted off the ground by the spider after having just been stabbed through the neck. It's just as horrifying as it sounds. This can also happen in-game if the spider gets you.
- The other children, whether it be the ones trying to kill you or their corpses, bring a lot of terror and Fridge Horror to the game. There is just something ominous about their mere presence, especially when you enter the part of the forest that is essentially a child's makeshift hideout filled with contraptions, traps, and the many dead bodies of other kids.
- One of the Easter Eggs requires you to walk into a dark cave and continue walking through pitch black, while cave critters chirp, in order to reach it.
- The many possibilities as to how you can die. At least, some of them are quick.
Nightmare Fuel / Limbo (2010)