I would love to see Ergot poisoning used on this quest.
Add some ergot infested grain heaps that are trapped to fall over and spill ergot infested dust into the area, causing confusion effect (or just gas traps)...
Or have a pile of grain covering a secret entrance to some back room of the Grainery or the treasure chest rooms, moving it aside requires a save vs ergot or you somehow suffer from ergot poisoning.
http://www.hbci.com/~wenonah/history/ergot.htm
Another possibility would be some sealed area that is trapped or unstable via the Lycopodium Powder explosion effect:
http://www.angelo.edu/faculty/kboudrea/demos/lycopodium/lycopodium.htm
Perhaps similar to the rope swings or other items that require a check, the "walk very carefuly throught the dusty and highly explosive grainery tube" or you get hit with a fire effect...
-n00m
Awesome idea dude.
Awesome idea dude.