Got a hilariously bugged damage bug with Large Sword. Destroyed Amon and the final boss. Use Large Sword's special attack (forward forward Attack) while getting hurt, but take damage while the special move is happening. Thinking this is because the invincibility wearing off messes with the move so the game still thinks you are using the move. You can use Fast Travel and it stays on. Die or reload and it goes away. You can even switch weapons and it stays on.