I think disease would be an interesting addition.
Imagine, you walk through a village, flies everywhere, doors shut with red X on it.
you can go in if you want, but the risk is high that you get infected, which would be lethal.
Also, you can have add a sithlord that uses a super-version of plague like Nihil's drain life.
PS. What does STD stand for anyway? I voted for the disease, but I haven't got a clue about what it means...