I would dearly like to cage trap a web-spinning forgotten beast (or other procedural creature, like a titan) so as to make a forgotten beast silk factory. (Yeah, I know giant cave spider silk is worth more. I don't care; having things made out of FB silk is awesome.) Unfortunately:

  1. All procedural creatures have basic trap immunity.
  2. The usual workaround for that, webbing on the cage trap, doesn't work because webspinners are immune to webs.
  3. Procedural creatures also cannot be stunned, so luring them into cage-trap-paved areas and attacking them doesn't (as far as I can tell) seem to result in them ever losing consciousness and getting trapped.

So, does anybody know of any methods that might work? Maybe circumstances where an FB might be rendered unconscious other than by the usual stunning? Or a strategy I'm overlooking? Or are they just uncapturable?

  • 1
    You can't harvest silk from a creature in a cage, so why bother? Just lure it into your factory and you're golden (Provided your factory can withstand their building destroyerness).
    – kotekzot
    May 7, 2012 at 20:47
  • @kotekzot: Having it in the cage makes it more manageable. :) But yeah, I suppose luring it into the factory is the remaining option. Challenging, that.
    – chaos
    May 7, 2012 at 21:06
  • I don't remember if caveins knock demons unconcious or not. May 7, 2012 at 21:11
  • @RavenDreamer That was my first thought, but wouldn't the cavein destroy any traps below it anyways?
    – SaintWacko
    May 10, 2012 at 15:51
  • Cave-ins don't destroy traps, so no. May 10, 2012 at 18:22

2 Answers 2


You're going at your problem the wrong way. You don't need to capture a Demon or Forgotten Beast in a cage trap to start a silk farm - all you need to do is trap it in an area such that it can shoot its webs but not otherwise bother you.

Mitchewawa on the Bay12 Forums has quite an extensive topic on this very subject.

The crux of it involves exploiting pathing and the fact that building destroyers cannot destroy hatches from below. Basically, you want to isolate your webber, then use caveins etc. then dig out a silk farm area based on where you isolated it, and finally, sacrifice a migrant to get it into the silk farm area (with the possibility of orchestrating a cave trap to seal it off again).


I used to have cave-in traps that were activated by plates, in turn activated by water. I put a pit behind a door, and the water activated plate in front of it, together with cave-in pillars beside with cage traps. The FBs used to destroy all doors, so this would let the water on the plate that would cause the cave-in traps to activate and hopefully stun the FB into falling to a cage. This, because some FBs were flying and didn't touch the floor to activate plates, but still did destroy the doors and such, so doors holding back water, potentially highly pressurized, was my idea to help launch the FBs into falling into cage traps. I think the cave-in traps were the most successful in capturing FBs, not that I ever did much with them, I did have a fort with 3 FBs in cages.

Another trap idea is to use weapon traps to cause jumping beasts to jump into adjacent tiles and traps therein. Won't work on creatures that have trap-avoid, but if you have spikes that rise from the floor due to frequent switching, I think this might cause even them to jump to adjacent tile and a cage trap therein, with luck. Anyway, weapon traps are great for keeping your fortress clean by causing invaders to jump into volcanoes and not litter your fortress with their junk, if you should provide them a convenien walkway along, say a magma tunnel, or volcano mouth where they can use their lives constructively to please the gods and not bother your fortress.

  • Very clever. For idea #2 I think a small fall should stun the dodging FB enough for it to be caught in a cage trap. Making enemies dodge into a volcano isn't very good, though - their iron items will not melt and the buildup of unreachable items will cause a loss in FPS.
    – kotekzot
    Mar 27, 2013 at 17:07
  • Many volcanoes are floored(at least partially) with SMR, which will simply vanish items that drop into it. Something I personally prefer is a dodge-me trap into a little "bucket" I can flood with a few drips of magma. Bodies and useless troll fur cloaks will burn away, leaving behind only handy-dandy iron gear.
    – Resonating
    Jun 11, 2015 at 15:06

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