There may have been an exception of two

Vivec made sense, you needed him to sort the God weapons and take out the big bad, but the guy I'm talking about was some, imo, random elf in a cave I had never met before in any playthrough. Killed him for whatever reason so "the threads of fate have been severed" screen came up prompting the reload. I still have no idea who the fuck that elf was or why he was important enough to warrant that when I could still go and complete the game and leave his hermit ass alone in the cave forever.