what this mod add's:

the music disc is a music used in wemmbu's unstable universe video usualy

and also adds a sword named THE FLAME like wemmbu's rivil flamefrags (the crafting recipe in the gallery)

and to get the music disc there is two ways:

with op :

/give <your name> wemmbu_music_disc:wemmbu

in survival mod :

you should go to a mushroom island and you'll find wemmbu there and kill him and you'll get the music disc and an advancement

why should you download this mod:

if you love wemmbu's content you'll like this mod