One of the interesting parts of Amnesia is how often you are actually safe. You never know it. Oh no, because that would defeat the purpose. It's just that there's a lot of time spent wondering if you are safe and when it will all start again. There's no guaranteed clues of what might make it all begin. Even the fleshy transformations won't necessarily indicate anything worse than a few rock falls. Yet a door opening and creaking can mean everything, nothing, or a sign of a trap.
Some horror games, especially roleplaying games, don't realise the importance of safety or the way it can just really build up anxiety and tension. That's why there should be no random monster charts in a horror game, at least not beyond the inspiration phase, as each monster should be carefully introduced with a trail of little clues and warnings to really milk all of its worth.
It is also one of the reasons why horror normally concerns itself with a single monster, or very few monsters, or one monster type, so that fear of one doesn't clash so much with fear of the others. Also, the more monsters you have, the more places you need to push them, the smaller the 'safety' net and the less time to build up anxiety.
So there you have it. Less monster time builds up more apprehension - especially if you drop lots of little hints, clues, and signs that maaaaaybe the monster will be here now. Maybe. Never let them be sure.