They can be added in the game with an editor, but due to their unfinished state they cannot be killed by the player. Spiders do appear in the Nave, but they don't attack and barely move; they're just for scenery.
- In the critters folder, there are three sound files, named "spider_die#.ogg" meaning that the spiders were meant to be legitimate, killable enemies.
- The arachnids were originally planned to feature as enemies Daniel would have to encounter in the Archives, but were dropped from the final game.
- Spiders appear in Penumbra: Overture, another game made by Frictional Games. Both appearances are nearly identical.
- Despite not being an enemy, they will bite Daniel if he gets too close.