I pulled it off with ten upright spike traps (with ten steel spikes each) placed in front of a wooden artifact door, linked to a lever and set to repeat. It looked something like this:
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Note the 3 spike traps closest to the door aren't necessary under ideal circumstances. There was a backup cave-in trap in case the spikes failed due to demon heat causing them to dismantle but it was unnecessary in the final run. Afterwards the dwarves built a staircase to hell and engraved the edges of the underworld map to mark it as under dwarven ownership.
However, this was back when I had a bad habit of force-quitting and reloading whenever something went wrong. The trap saw multiple redesigns until I finally got it right; there were a few attempts where heat did dismantle the traps after a fire demon lingered too long, and several where the demons simply lost interest due to smoke from the door catching fire. (A non-flammable artifact door would be preferable.) There was also one unsuccessful attempt to simply handle it with soldiers where they fought valiantly but were eventually overwhelmed.
I can't recommend playing that way; a fortress that sees only flawless victory is left with no good stories to tell. I could have accepted the loss of my soldiers, had the dwarves retreat further into the caverns and designed new traps after the first ones failed, picking off the scattered demon horde bit by bit through guerrilla warfare until the dwarves could finally reclaim their fallen and send freshly trained soldiers into the heart of hell seeking vengeance. That would have made a good story regardless of the outcome. As it stands, I erased every sign of struggle that gives weight to the eventual victory, leaving me with a successful but ultimately dull fortress and a bit of knowledge on trap design.
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Topic: Swampcavern vs. Devils - Spoilers (Read 3167 times)