I love survival horror games. Ever since I first played Resident Evil on the original PlayStation, survival horror games have been a staple of my gaming diet. And what makes an effective and successful survival horror game for me is not so much the jump scares sprinkled throughout each game, but more so the way developers use disempowerment, tension, uncertainty and fear of the unknown to provide thrills and chills.
An aspect of this psychology that some videogames successfully implement is occasionally what you can see in as much as what you can't. For example beings, creatures or monsters that can at first appear harmless or dead (but are actually dangerous) help add to the fear factor and overall creepiness of a game.
Here I have compiled a list of passive and unpredictable creatures and monsters that I have had both the pleasure and misfortune to encounter in some of the horror games I've played.
Please be aware there are quite a lot of spoilers in this list.