I don't really know where to post my creation but I think the General Discussion is a good start.

So to start, I made a mod for STS that changes the music, battle, menu, UI FX, to work in tandem with the Steam Workshop mod The Wild Card by Darkglade.
It is still very WIP (music has looping issues) and i'll continue to work on it because it's a fun thing to do during Quarantine
Link to the mod and how to install it:
https://www.nexusmods.com/slaythespire/mods/4

Yes I'm using Nexus mod and not the Steam Workshop. I don't know how to utilize the mod loader and implement my mod to it so for now this mod permanently changes the file. If someone knows how to do so please teach me :)

P.S AFAIK, this seems to be the only mod that changes the music of the game. IDK if other mods do so but my mod doesn't change how the game works, only how the game looks and feels.