The Beast Must Die (?)
No idea about how underrated these are, but these are my favorite - and I'm big on niche thriller/horror and typically only read 9+ in BL:
Dreadful Night https://www.mangago.zone/read-manga/dreadful_night
Black Mirror https://www.mangago.zone/read-manga/black_mirror
Not that one y-y
Neither of those too, unfortunately (in alr saving those for later, but thank you)
I remember seeing someone name drop a supposedly very much underrated bl (manhwa i think??) some months back. Genre was thriller/horror if I'm remembering right, don't really know the plot since i never read it tho
I do think the rating was high, probably around 9? Anyway, would really love it if someone could find it for me