So Nutscaves pulled through the recent tragedies, though we still have over a dozen dwarves wandering around slowly with fever and extreme swelling. Ticking time bomb or totally safe? Hard to tell.
With the autumn siege of 267, combined with hauling all the previous goblin crap to the trade depot to buy all the iron the human traders brought--Armok has realized there is a problem.
The problem is that the goblins and their buddies (trolls, namely) just bring too much crap to the fortress. The particular goblin civilization that attacks Nutscaves, The Tame Disloyalty, does not have good access even to the weakest of metals. Most of their troops arrive wearing a low quality, emblemmed copper breastplate and helm, with low quality troll fur or spider silk clothing to fill in the rest of their "armor". Their weapons are usually copper. Their veteran goblins wear the same, but sometimes have a silver weapon. The masters and captains usually wear a few pieces of iron or steel.
I've seen other goblin civilizations, such as the one at my last fortress, that can afford to outfit every last goblin in full steel. So I know it could happen. But at Nutscaves it doesn't.
Armok added the masterwork copper and bismuth bronze menacing spikes that Sarvesh, our now-legendary weaponsmith, skilled up on, to the entrance spikes. (I couldn't melt the darn things..she'd tantrum.) This beefed up the spikes a great deal, especially considering that even our best-armored foes are usually wearing mere cloth over most of their bodies. (And the traps I beefed up had been just small sets of wooden training spears, before.)
As a result of the upgrade, we're getting a lot more corpses a lot faster during sieges as a result, and the resulting heap of bloody cloth outside the fortress is becoming...mountainous. It's getting difficult to drag it just the thirty paces indoors, to the stockpile next to the trade depot, in any reasonable amount of time. Then the junky goblin armor consumes a lot of bins, and the spider silk stuff is annoyingly valuable, making it hard to trade it all away.
Hauling it down to the magma has become a bit problematic, because Armok is sometimes having to use dumps to store other unwieldy things Armok accidentally overstocked, like magma-safe hatches and pump components. So I have to make sure nothing else in the fortress that I want to keep, is marked for dumping when I send items down to the sea. I'm a little overwhelmed with the level of micromanagement needed to get rid of all this junk.
There is enough of it that the trade depot filter screen is getting a little slow--something I had proudly prevented until recently. I enjoy keeping my fortress interface running smoothly and at a good framerate, and having the filters respond quickly to keystrokes. There's way too much crap in the fortress now.
There are several possible solutions I've considered:
1. Don't let the goblins enter the map. But Armok likes the goblins. The goblins give us purpose, meaning, and most importantly, entertainment in several forms.
2. Who cares about the items I might accidentally destroy...I can always dig up more quartzite and replace them. There's at least one whole rock level of it under us that hasn't been dug out. But Armok hates digging and (s)he hates the possibility of dumping some masterwork item while the fort is currently at its unhappiest since the Tantrum Spirals of Wiping. Armok can take this solution but Armok would like something better.
3. Armok was thinking to him-/herself: "If only I could set up a trap that sorted out the steel and iron items from the goblins, and dumped the others into the magma--"
And then it dawned on Armok. A substance in the fortress exists that can do just what Armok desires! It is the preferred substance of the best and mightiest builders: the magma itself! And Armok finally understands why the great builders would go to such lengths to utilize this substance!
Magma kills goblins and trolls, and all their other buddies that sometimes come along. It burns up everything they wear except iron and steel. When drained, it leaves nearly-molten-hot iron and steel items--but they can be cooled by being dunked in water.
Armok has theoretically infinite access to magma. Armok has infinite access to water. Does Armok dare build the deadliest trap Armok has ever seriously conceived of?
Previously the spikes were the deadliest trap Armok had ever dared employ. Just a few months ago, a veteran dwarf soldier in full fortress-forged, high-quality steel plate was accidentally killed by one in a single hit. (Oops.) But other than that, Armok has successfully kept the dwarves quite safe from the spikes. Can Armok keep the dwarves safe from the magma?
There is the question of what type of trap to design.
Trap Design 1. Some builders bring their magma to the surface and flood their entry bridge with it, then atom-smash the magma to drain. Armok could do that, but in Nutscaves it would be very tough. The holes in our aquifer aren't big enough to fit more plumbing (the current "surface" magma rests two layers below the aquifer, powering the forges), and Armok's magma piston isn't currently reusable either, after the Great Collapse of 263. Making the magma piston reusable once more isn't a huge deal, because it just involves some building, and extending water plumbing that was designed with this type of extension in mind. But, Armok would have to deconstruct an awful lot of stuff and tear massive holes in the top of the fortress, to freeze large enough openings in the aquifer to fit plumbing. This would probably take several tense winters of carefully-planned building.
Or I would have to painstakingly open the aquifer the "normal" way, with pumps, after carefully deciphering a diagram with lots of ASCII symbols, and which wasn't drawn with readability or order of operations particularly in mind... Haha, yeah right!
Armok has not particularly enjoyed freezing through this particular aquifer--Armok has done it twice now, once to make a path and the second time to widen it. (It's annoying because the aquifer is two layers tall, and it's several layers below the surface, and it has to be frozen-through in a funnel shape. The "funnel" I had to dig just to wind up with a 3x3 stairway in it was massive and very disruptive to fortress traffic.)
Trap Design 2. I could build or remodel a room below the aquifer, capable of being filled with magma, and drained, and then cooled with water. (Alternately, I also have a "room" in the fortress that is full of magma, and conveniently placed at the bottom of a hundred-ish-story air shaft. It could be easily modified to be drainable and refillable.) Then, all prisoners that behave themselves (non-thieves) could be melted in there--and I wouldn't have to bother stripping equipment from those types of prisoners anymore either. Unfortunately my current trap system (due to being very lethal) only allows me to pick up about a dozen prisoners from each siege, though, and I like to use prisoners for soldier practice. (It's the non-prisoners I want to melt.) During sieges, another two dozen goblins-and-co. tend to die to one of the two strips of spikes, or weapon traps, and the rest run away.
Trap Design 3. I could simply kill less goblins. I could remove high-quality metal components from traps, and stop spilling so many of the attackers into the spike room below the drawbridge. This would reduce the amount of clothing and other general crap I wind up with. However, my common sense tells me that decreasing defenses in order to potentially allow more or stronger attackers to get into the fortress, is not the smartest way to deal with our little trash problem.
Trap Design 4. I think what I'd really like, is to be able to flood the spike room under the drawbridge with magma at will. (While also retaining the ability to decide whether or not to use the magma, such as if I want to keep a special corpse for butchering, or some piece of treasure.) This would mean removing any weapon components in there that are not magma-safe (not a problem--hello Sarvesh!).
Getting water in there to cool it afterward would be a real pita, though, because the area is considered "Above Ground", and water will freeze as it enters the room at frozen times of year, which sometimes happen to correspond with sieges. The freezing water will create an ice plug, jamming the whole system.
The tiles of my spike room are considered "Above Ground" because the natural rock above them has been removed (when the drawbridge was built). (Even if something is built above "Above Ground" tiles, they can never become Subterranean again. It's similar to being infected with dreaded Light.)
So what I need to be able to do, I think, if I want to be able to melt the prisoners that get dropped under the bridge--is to find a way to lure them into a Subterranean area that can then be sealed (and then flooded with magma, drained, and cooled with water). Luring them (such as with a chained rabbit) would need to take into account that they may have long-range weapons, and one shot can potentially kill the lure, stopping it from working.
I've thought about using a locked door to protect my, say, chained rabbit from real harm--since that's what I use to get my giant cave spider to shoot silk at that poor dog in the weavers' area. I believe the goblins can either unlock doors (because they're sentient), or that they just won't bother trying to path through one (and so won't be interested in the rabbit), though. (In 40d it was the latter, but I've read on the magmawiki that it's the former, and magmawiki has been wrong so many times--so I don't know this for certain until I test it myself.) Well, I don't think a locked door will be right for this.
I remember a trap design I saw in 40d where a goat was tied up at the center of a long spiral path. As invaders entered the path, a floodgate went up to protect the goat, and the invaders got doused in magma. This is effective against goblin archers, and I use a design based on it for my trade depot entrance. It does have some problems, though, like it's kind of slow. (Goblins don't just charge in.) And in 31.25, unlike 40d, pathing is blocked by 1/7 depth evaporating magma. Magma takes a really long time to evaporate.
Well. I'll think about it some more.