Tenebrous

really quick, there's a new version out! a sequel of some kinds. I personally think it's better, so give it a try!
here's the link: https://www.curseforge.com/minecraft/modpacks/tenebrous-ii

Tenebrous is designed to create a darker, hopefully scarier, and slightly harder experience out of minecraft. Although minecraft's foundational elements have been unchanged, the combination of mods in this pack is designed to make minecraft gloomier. This is not a cheery world, in fact this place wants you just as dead as the skeletons that roam the caves. But you can fight back, and eventually the world will not be as scary as it once was.

This doesn't mean it's any less dangerous, though.

By using over 70 mods this pack succeeds in giving minecraft a much more dark fantasy/gotchic aesthetic. Even if it doesn't scare you, it at least provides an interesting theme that is sure to clash with the majority of mods and modpacks that exist out there. A few honorable mentions are:

Ambient Environment
Born in Chaos
Cave Dweller Evolved
Enhanced Celestials
From the Fog
JourneyMap
Majrusz's Progressive Difficulty
Sound Physics Remastered
The Graveyard
and True Darkness, just to name a few

I understand that having a modpack containing 70+ mods is a big ask for many players, but keep in mind that I wanted it to still feel like minecraft deep down. So, I avoided mods that make things too complicated. This is another way of saying that if you like magic or tech mods, you've come to the wrong place.

For now, I hope you enjoy the unique theme of Tenebrous. Happy hunting!

P.S it's recommended that you use optifine for the best experience. I also recommend that you use Gray's Mob Overhaul to make all the existing mobs more fitting to the aesthetic.