inscription #8 tell the truth ? It says "I kill and #9
so it can't be true, because it says that it kills, which - if true - would
mean that it contains a piston, which would imply that it lies :
that's a contradiction, therefore, it lies and contains a
piston or is empty. Since it lies, either it doesn't kill (meaning
it's empty), either compartment #9 isn't empty, or both.
If compartment #8 were empty,
we couldn't logically decide whether the second part of the
sentence, "#9 is empty", is right or not. That would mean
that the Riddle would be insolvable, and this is why Batman
asked if compartment #8 was empty. But, I replied that
the maze could be solved if I answered Batman's question,
so that means pillar #8 contains a piston.