This is a resource pack that requires Polytone

This resource pack changes the atmosphere of Minecraft, making light during day considerably darker and nights completely pitch black, aswell as changing the colors of water, fog and sky to dark and muted sepia tones. This look is maintained across all biomes (even modded ones) to give the world a consistent eerie and oppressive atmosphere.

This pack is designed to be used with my modpack The Darkwoods, but it could also work well with a horror, apocalyptic or dark fantasy modpack.

I also highly recommend using the Fog enhancing mod Fog Looks Good Now, aswell as any mod or shader that adds dynamic lights to make the pitch black nights and caves a bit more endurable.

(note that some shaders might break some features)

Features:

Daylight seems considerably weaker, with noon being the brightest time of the day, and progressively scaling to complete darkness during the night. (Note: this doesn't actually affect light levels and mob spawn)
Light from torches and other blocks looks warmer and more intense.
Subtle white ash particles are always present floating across the overworld.
Clouds, Sun, and Moon textures have some tweaks to fit better with the atmosphere.
Grass and foliage colors are darker and monotone.

Credit for the idea: A_Shfox

Even though it was made with 1.20.1 in mind, it should work for other versions supported by Polytone, but I don't reccomend using it for versions past 1.20+ since some Polytone features are unsupported in newer Minecraft versions.