Okay, so I had an idea I just had to share...
How feasable is this as a deathtrap idea? The idea is to cage an absurd number of felines (100 should do) and station the cage in the entryway, like... Well, like so.
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.__________________________________=
<................................._|
<................#................_|
<................................._|
.__________________________________=
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< marks the direction of entry, possibly ramps.
. is smooth floor, of course. (Ripe for the engraving afterwards!)
_ is a pit. (Underneath this bridge should be a drop into several Z-levels of water.)
= is a wall.
# is the cage.
| is a drawbridge which retracts to the right. (It is depicted as raised)
Once you've gotten your cages set up (and you might want backup cages full of felines,) you go to the raws and set up the Thermonuclear Catsplosion. Wait until the gobbos or elves or dirty humies are in the entryway, then raise the drawbridge. (You could also just lock doors.) and pull the lever that sets the cats free.
See, what I'm, thinking is that cats in cage traps will be static - their heat won't matter. Once they're released from the cage, they react with the outside world, with predictable results, going thermonuclear. Their flaming kitty parts fly all over everywhere, including (hopefully) a nice ka-splosion outwards that flies out into the world (for coolness' sake), and enough falls into the water below to flash it to steam, thus adding to the bellowing smoke of doom that should be filling the corridor and belching outwards.
I'm pretty sure it'll work, once, and probably not even harm the fort, so long as you don't have a water channel access that the flash-frying steam can back up through. Big questions involve how do you mop up the mess? Will burning kitty parts just rot away into miasma after awhile, dissipating their heat?
It occurs to me that you could modify the design as-follows for maximum sadism:
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<|_..............................._|
<|_..............#................_|
<|_..............................._|
==_________________________________=
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This way there's absolutely no hope of escape for anything at all - if it's in that death chamber when it goes up, it's gone. Additionally, would heat the fort all winter. And spring... And summer... And fall... And winter again. Would it work if the cage to be opened was underneath the water below - an instant boiling effect to steam the bastards to death instead? (Or even just on a 1x2 platform suspended in mid-air from a support below the main bridge, to toss all the kitty bits off without exposing the gobbos directly to it, to draw out the pain and suffering.)