Today was a glorious day in CudgelDye.
The entrance to CudgelDye is an excessively large and overengineered deathtrap, consisting of a series of 9 3X10 tile retracting steel bridges over a 9 wide, 90 long, and about 20 deep pit that empties into the lowermost chasm level. Above the bridges are openings leading to large reservoirs of magma, and flanking those are large water tanks that can also be dumped into the pit. Depending on which levers I tell the dwarves to pull, this entrance way can kill invaders by dropping enemies 20+ levels, or by flooding them off the bridge with magma, or even by encasing them in obsidian. I originally built it to deal with the demoness rules of the local goblin civilization who appeared to be impossible to kill by any means short of an obsidian trap. Since then it has dealt with many goblins.
The caverns under CudgelDye are inaccessible from the fortress or the surface. I have been very careful while excavating the massive pit beneath the entrance bridge to avoid the creation of a walkable passage from depths to the surface. By breaching the top of a cavern, then releasing alternating floods of magma and water into the open area, I created a solid plug of obsidian to bore down through. Every use of the magma flood system is timed to match an incoming siege, so every tile of obsidian is created through the death of invaders. I eventually plan to make blocks out of the goblin-flavored obsidian so created to make a vast aboveground fortress, but that's a long-term project.
Leaving the caverns inaccessible means that forgotten beasts pile up. I have built an automated kitten dropper to explore the caverns, but otherwise did little to deal with the monsters. I was considering building a specialized cavein trap to kill them, but then decided that the gigantic entrance deathtrap I built to kill the unkillable demon queen could work on them as well.
I very carefully built a passageway, sealable with a retracting bridge, from the fortress entrance to the depths. Then I locked the inner doors, leaving only my trade chamber full of chained war elephants accessible from the outside, and waited. Soon four forgotten beasts were climbing up the twisting stairway from the caverns to the entrance.
What I didn't expect was what happened next - an eleven trade caravan arriving on the map and making to the entrance just before the forgotten beasts arrived. The elves found themselves trapped between the forgotten beasts and the trade entrance. They fled for the trade entrance, only to have the inner drawbridge slam shut just before they reached it. Then I pulled the lever to release the magma. The elves were incinerated, of course, and three of the four forgotten beasts died in the magma flood. The fourth has horrible injuries but is somehow still alive, I expect another magma flood will either finish it off or knock it off the bridge.
While this carnage was going on inside, an elven diplomat arrived outside. Followed by a goblin siege. The goblins finished off the elf, and are now marching on the entrance where the last forgotten beast is waiting. I expect they'll arrive just in time for the magma chamber to be recharged.