Is there any way to make a script in a room trigger whenever a monster (any monster) steps on a particular square rather than when a particular monster steps on a given square? Is there a way to make a script trigger when a given set of two blockers/objects/the player/whatever are in the same square even if they have both been moved from their original squares in the room?
Option 1 could use a unique trap. Put it on Floor 50 or something and make it special="1" and craftoutput="1" to keep it from random-spawning.