Guess what dargndorp says is probably the best solution for an experience of one evening.
I can recommend you to write down some particular words you'd like to use to create a
dense dungeon exploration atmosphere, simply words or terms you would rarely / scarcely
use in everyday language, but which rather serve this particular purpose well.
Most likely this will be adjectives of some sort, but I can also think of old medieval words
and sayings you could include (for instance the ghost in Lom Tranar could use such an
accent). Dunno... I only played so far as a player in an english speaking group, but I
haven't had the opportunity to gather too much EXP as a GM.
However, hope this helps.
Cheers,
MH+