My fort had been visited by a few flying beasts that came up from the depths, but I had fortunately walled off all connections to the underground caverns as I dug past them in search of magma. The dwarves were, however, rightfully worried by the arrival of a giant zombie ettin, a humanoid with two heads. Had it been living the caravan would have easily felled the beast, but zombies don't die...
The zombie was held at bay by two caravan guards while the rest of the merchants escaped, and suffered grievous damage in the process, but was still ambulatory. After this, two goblin ambushes had the pleasant experience of running into the Ettin; they were dispatched far more quickly than the caravan guards, even with the Ettin in a weakened state.
This fortunately bought the dwarves enough time to build a line of cage traps to catch the beast. It finally lumbered through the main entryway, emitting a foul miasma everywhere it went. It triggered a series of rock fall traps and weapon traps which seemed to have no effect. A Dwarven Atom Smasher was next employed for defense, but was dashed to pieces as it came crashing on top of the monster. Finally it stumbled right into a cage trap and was quickly locked away. Everywhere its cage is stored is quickly overcome by the foul stench.
So, now what do I do? This beast is destroying my framerate. I tried dumping it in magma, but the ettin grease stayed in the magma for months emitting a miasma and refused to go away. The dwarves won't build a cage under an atom smasher, and I'm not sure how to be rid of the beast. As long as it is present I think its mass of wounds will forever warp the very fabric of space-time itself in its near vicinity.
Any ideas or suggestions?