I dunno if the game itself would actually be too difficult, but how about the original Thief: Dark Project (or the updated re-release known as Thief Gold)?

It's not really a horror game necessarily, but the tense atmosphere of sneaking around and avoiding guards who can rightfully kill you in combat due to being better trained, as well as a few levels that are outright horror inspired, should be interesting.

That being said, if you're gonna play, I would suggest playing it on Expert - not because Normal or Hard are too easy, but because Expert forces you to explore more of the level and get more things, putting you more at risk of dying, and also restricts you the most as far as your behavior (no killing humans is the usual rule)
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Disagreeing with your criticism doesn't make me a fanboy; disagreeing with your praise doesn't make me a hater.
Fighting over this is self-destructive.

Need some help with Youtube stuff.

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