That entire menu thing is mainly me testing main menu changing depending on game progress. As you said, all the lore is not in the game yet so it doesn't make sence yet, but will in the future. There is already some dark stuff in the game if in some specific bestiary entries, mainly the ghouls and abominations.
Being able to change between menu styles is doable, but I'd like to add atleast one more background before I do that.
Also, the menu music is royalty free track from youtube: