shilsen
Adventurer
Things that they (a) can't immediately identify and (b) aren't sure how to deal with. A big tough monster is still straightforward - the PCs fight it and win or lose. But a situation where the PCs aren't sure what they're facing and even more importantly, can't deal with it by charging in with fireballs blazing is always a difficult proposition.
There was a great thread started here a few weeks ago on creepy situations which is a good case in point.
There was a great thread started here a few weeks ago on creepy situations which is a good case in point.