[Den]

The lever was originally attached to a rope, and the stone block was used for grinding grain into flour. Teams of workers would raise and lower the lever and reset the stone block, so the next batch of flour could be made. Obviously, with the workers long gone, the rope either got stolen or disintigrated with time, so now it has to be triggered manually... which happens to be where the grain was originally turned to flour.

Why is there a series of stones that, when stepped on, causes poison darts to shoot out of the wall?