20. Trick Stairs
 
A staircase goes down about 10 feet and 
ends in a small landing with a door facing 
the stairs. The steps are made of flagstones 
set in mortar. The flagstones are loose. 

This staircase will become a slide if the
door to room 21 is NOT opened properly. A
thief may NOT detect the trap, but a dwarf
could detect shifting stone if checked for. If <66 2/3% probability (d6, score 1-4)>
the door is opened without 1st locking a
secret catch (detectable only by a thief), the
stairs suddenly slant, creating a steep
incline. Unless previous precautions have <Slopes, WSG>
been taken, characters slide into room 21,
automatically losing surprise && initiative
for the 1st round. Characters roped  <Roping Together, DSG/WSG>
together, but not fastened to anything, have
even greater difficulties (the characters will
be surprised for 2 segments and may NOT
take any action during that Time). After the
door is closed && pressure released from
the slope, the stairs return to normal. If the
door is opened after locking the catch, nothing
will happen and the party will find stairs
going down.

>>21.