Update: Took me a while to come around, but I've made some tweaks and lowered the sound of the music as I felt it was too loud. I'll also have some other projects on the way on a slightly larger scale than just a few edits to 1 trial. And yes, it'll be more Star Rail music.
Since I've waited for someone to possibly try something like this, I decided to look up a guide to try my hand at making this. This is my first mod I'm uploading and I hope you'll like it.
As the title states, I've swapped the themes of both phase one and two of "The Final Day" with both the instrumental and vocal versions of Wildfire and A Trap With No Return from Honkai: Star Rail. Both are also edited by me as well to try to get it to loop. The edit is anything but perfect, but I'm fine with the results and liked how this turned out in-game.
I'd recommend using Penumbra for this.
Make sure you enable this mod in default collections in order for this to work.