Just an idea I have. Could a game that has the following traits work?

1. Game has a horror theme. This, of course, includes the scary things that you would expect from this sort of theme.
2. Game has unfair death traps; doing reasonable things will cause you to be killed and sent back to the last checkpoint. (Assume that checkpoints are frequent and not in places that would cause you to be stuck. Also assume that, unlike survival horror games, there are no limits on saves or resources to worry about.) I'm thinking something like Syoban Action here.

Do you think this combination would work? Would you consider playing such a game?

For me personally, no: I enjoy neither the horror genre nor systematized unfairness. Others' mileage may vary, however.

It sounds like a horror themed puzzle game where you keep dying until you figure out what you're supposed to do. Why not? There are puzzle games where you keep failing until you figure it out. But imho this would work better if there are some hints that tell you what to do. That is, it should be possible to discern that some of these "reasonable" things are not to be done. Then a good player who enjoys figuring out puzzles is especially rewarded for figuring a section out without ever dying.

On the other hand, if the deaths were really random and you had no way to avoid them without pure luck, then I probably wouldn't like to play such a game for long. Maybe for a few giggles, but it'd get old quick.

Yeah, you lost me with the unfairness bit.

If I wanted unfairness I'd be out in the real world. I play games to get away from shit like that.

If you went back twenty years it would work.
Or if you heavily market it to these 'streamers' people are always talking about.

Ditto, especially the bold part.

That said, some examples of "unfair death traps"?

Google rick dangerous. There should be a free download. That game is the very example of your 2nd point. Play it a bit to get the idea. And then try to imagine changing image to be more suitable for horror.

I'd say, after some unfairness, the horror doesn't even matter anymore

It's called Knock, Knock.

I'm not sure if it's horror. I'm not even sure if it's a game / has gameplay. But I found it pretty fun / compelling in its own right.

Sounds like a die-and-retry game with horror theme. Could work if the "bad ends" are entertaining enough, I guess. Many adventure games play on the see-your-character-die humor. I mean, there are even games (like Long Live The Queen or Corpse Party) where horrible character death are collectibles achievements

But I think if you know you can't avoid dying until you fell into a trap once, there would be very little tension after a while. So the horror would fade, and begin to be a "hey, let's see how this moron will bite the dust next" silly entertainment, like some sort of grimdark monkey island. Just the way you don't really care about the random stupid teenagers/future corpses in a typical slasher movie, start making fun of them, and the movie has to rely on cheap jumping scares rather than real horror.

Minus the checkpoints, isn't that basically the first Alone in the Dark?

Yup, that pretty much fits the bill : Unless you knew what was coming, there was pretty much no way to avoid getting horribly slaughtered by lovecraftian horrors. You learn that in the very first room, where you have to blockade a random window for no reason otherwise a monster will jump in and you won't leave the room alive. And yet, it was a fun game. So the combination works, at least for me :)

Shadowgate! "There are 3 mirrors to break. Two of them will kill you for doing it."

The Immortal comes to mind.

So lots of dying and retrying until you get past each trap? I fear that would render the horror theme moot, except if all you want from the horror theme is the aesthetics.

On second thought, it might actually work if the 'gimmick' is that you die in a comically gruesome manner, with several possible variants for each trap. In the same sort of fashion as Happy Wheels.

Sounds like Spooky's House of Jump Scares to me.

As far as point 2, that sounds like a really bad idea unless it's done in a humorous, think-outside-the-box way, like in the Humbug series of online platformers.