So it's a bit more mainstream but I'm putting it here anyways, Slender: the Arrival was GREAT and I feel like people only really know about the demo for one, imo, insignificant level that was greatly improved upon in the Arrival. Lots of love put into that game. If you haven't played Slender the Arrival, it's probably worth your time! Also, Harvester games has a bunch of fun games. I'm personally still playing The Cat Lady as my entrance to games by this developer but I enjoy it greatly. I do have some beef with them though because you cannot access the original version of Downfall anymore, at least not when I last checked. Lastly, while it doesn't meet the indie game check, I do think anyone that likes indie horror games would really enjoy a lot of the Silent Hill franchise. I recently finished the third game and it's great! I recommend starting with 2 because it is a bit more separated from the main plot and works as a standalone, but if you aren't intimidated by how many games there are, the first one is still great. Be ready to have to think a lot and in abstract ways for Silent Hill!
Edit 6/21/2023- Not out yet but also one I am SO excited for: The Hungry Fly. It's a low poly poetic horror game about being a starving fly eating rotted food. It's supposedly going to be more on the dark and depressing side, and is meant for the player to relate to and realllly take in. Given my name is Maggot I am not sure how I forgot this title because this game looks made for me ahaa

Cat Lady is definitely a favorite, but I also really like the developer's other games.
Downfall is amazing but impossible to play for people with eating disorders, so watch out.
The newest one, Lorelai, is the best one in my opinion. All of them are just amazing in terms of story and psychological horror. Lorelai's situation is a very realistic one, and I could see these series of games spreading awareness about mental health issues. That game has gotten a lot of criticism for not running well, though.