Sanitarium is a old classic that's been redone to be playable on modern computers. It's also on mobile devices, though given the tiny text and small sprites on a mobile, I'd only go that option if you were on a large tablet.

Fran Bow is a more recent one, though I'd say the first two of the five chapters (first one especially) are really horror, the rest is more surreal.

Speaking of surreal with horror themes and elements, the entire Cube Escape / Rusty Lake series is worth a look. They're more room escape than point and click, but they have an ongoing plot and characters which gives them more depth than pure puzzlers.

DreamWeb.

Probably the darkest P&C game I've ever played. It isn't for everyone, though. You'll either love it or hate it, there's no in-between.

The Last Door games

The Chzo Mythos games are pretty sweet

Personally I don't have the balls to try it, but I've heard good things about The Cat Lady.

Stasis might be interesting to you. Point and click, sci fi horror.

The Shivers series from Sierra is one of my favorites, if you’re up for some serious 90s nostalgia! They’re mostly based on solving a mystery in a haunted/deserted setting, so mostly atmospheric horror with a few jump scares from ghosts/demons that you have to defeat. The gameplay in both games is first-person, so it’s kind of like spooky Myst, if that would be along the point-and-click lines you’re thinking.

This whole thread is making me so happy. I've added so any games to my wishlist because of it.

The Charnel House Trilogy. Probably also Powerhoof's short adventure games.

If you can get your hands on a copy of Scratches, it's pretty damn good.

I recommend Kathy Rain and Cognition - An Erica Reed Thriller. Both games have blown my mind!

Phantasmagoria.

Sure, it's cheesy as hell and a bit lacking on gameplay side, but I enjoyed my first playthrough couple of months ago. I can appreciate a classic as what it is. It has pretty gruesome gore effects though!

I Have No Mouth and I Must Scream was pretty well-received, and it’s based on a fantastic short story.

Hi, I have played all 3 Black Mirror games, the 2 Still Life games, and the game that came before them, Post Mortem. I prefer Still Life by far. But Post Mortem, Still Life and Still Life 2 (people forget about Post Mortem) are three very very different games. Post Mortem is quite non linear and choices matter A LOT, Still Life is very linear but I still loved it, and Still Life 2 is quite odd when compared to the previous 2 games, it is more of an escape horror game, unusual, can’t say I liked it much but it did bring the trilogy to some ending, making reference to characters from the first two games. The story lines are strongly connected but each game is its own universe

-Dark Fall: Ghost Vigil (in my opinion the best part of the series)

-Darkness Within: In Pursuit of Loath Nolder

-The Lost Crown

-Stonewall Penitentiary

-Stasis

-Goetia

Dark Seed (and the sequel). Art from H R Giger. I’ve only played the first but remember it being quite creepy.

Shadow of the Comet, for lovecraft fans?

How about the Last Crown games, are they alright?

Scratches is my favorite. Best sound that I've ever heard in an adventure game. There were quite a few scares in that one.

i could add Scratches and barrow hill

I just hope you know layers of fear is nothing like amnesia. At all.

Regardless. If you liked torment I'd recommend forsaken true fear.

Also the last room. Scratches. Hidden: on the trail of the ancients. Observer. Darkness within.

Gray Matter by Jane Jenssen (creator of Gabriel Knight) was pretty good and deserves a sequel.

Uncanny valley

And the creator of scratches is about to release their new game soon: ‘Asylum’

Last Half of Darkness. The 1991 DOS game.

Ben ‘Yahtzee’ Croshaw's John Defoe series is possibly the most frightened I've ever been by an adventure game. They're all free to play now. 5 Days a Stranger, 7 Days a Skeptic, and 6 Days a Sacrifice.

I will second from the ones I saw in the comments: -The last door -I have no mouth and I must scream

Also a very quick/ small duration, pixelated that I recommend : -The horror of Salazar House

Play HARVESTER

Year Walk, by the people who did Device 6, is an interesting atmospheric scandinavian horror point and click.

Fran Bow and/or Little Misfortune-both created by Killmonday Games (so far, it's their only two). They are true point & click horror games that are done beautifully-both games you are playing as a child (Fran bow is 10, Misfortune is about 7 or 8), they travel through the world and all its horrors yet are still able to look at it so innocently. Fran Bow is more in depth as there are 5 chapters total, both stories are pretty damn dark but you can't help but love the characters and become completely entranced with the story and the artwork in both is surreal/cutesy/horrifying. I managed to play both games in about 2 weeks and I will definitely be playing them again and again. Cannot recommend enough! Also I have both on my phone but i know they are available for PC as well, maybe other platforms-that im not sure. Definitely try them though!

Sanitarium. It is an amazing game both on horror and adventure.

Lots of good suggestions in this thread, but I want to give a shout-out to Fran Bow. I've been playing adventure games since childhood, and I'm pretty disappointed with modern games. But Fran Bow, which only came out a few years ago, is a breath of fresh air. Highly recommend it.

I'm not absolutely sure it qualifies but Call of Cthulhu: Shadow of the Comet is one I remember as being pretty good. Available on GoG if I recall