The tower

What it is

Somebody scanned a tin of tomatoes, and now it guards floor 91.

Every creature anyone has ever found is standing in the tower, five to a floor, weakest at the bottom. None of them were invented for the job. They were found in kitchens and corner shops and the back of a cupboard, and they have been put to work.

The tower is sealed the day it opens. Nothing found afterwards gets in — those wait for the next one. So the tower never gets any harder, and you do, which means every floor in it will fall eventually. The only questions are who, and how fast.

There is a top floor. Above it, the same five come back a little stronger, and then again, and then again. Nobody has found out where that stops. We know, and we are not saying.