Traps and Pits Costs

Structure Pits and Traps Costs
Pit, open earth (10’ x 10’ x 10’) 20gp
Pit, open tiled stone (10’ x 10’ x 10’) 500gp
Pit, camouflaged trap door By size +1,100gp
Pit, spiked By size +100gp
Trap, arrow 400gp
Trap, bricks from ceiling 1,200gp
Trap, poison dart (purple worm poison) 1,880gp
Trap, poison needle (purple worm poison) 1,620gp
Trap, portcullis 750gp
Trap, rolling rock 1,200gp
Trap, scything blade 360gp
How these were derived:
Pit, stone: a 10’ x10’ x10’ dungeon excavation = 500gp
Pit, earthen: a 10’ x 10’ x 10’ moat = 20gp
Pit, camoflauged: A shifting wall (1,000gp) and a trap trigger (100gp) = 1,100gp
Trap, arrow: An arbalest (50gp) + a secret door (250gp) + a trigger (100gp) = 400gp
Trap, bricks from ceiling: Bricks (a mass of stone equal to 5 stone doors, 100gp) + a shifting wall (1,000gp) + a trigger (100gp) = 1,200gp
Trap, dart: A crossbow (30gp) + a secret door (250gp) + a trigger (100gp) + poison (1,500gp) = 1,880gp
Trap, poison needle trap: A lock (20gp) + a trigger (100gp) + poison (1,500gp) = 1,620gp
Trap, portcullis: 3 metal doors to represent the portcullis (150gp) + a secret door (50x5x2 = 500gp) + a trigger (100gp) =750gp
Trap, rolling rock: A big rock (100gp) + a shifting wall (1,000gp) + a trigger (100gp) = 1,200gp
Trap, scything blade: A large pole-axe (10gp) + a secret door (250gp) + a trigger (100gp) = 360gp
Things I didn’t take into account:

  1. The attack throw of the dart/arrow trap thrower
  2. Reloading and re-setting of the trap; is it automated or single shot
    Please let me know your thoughts. Unlike most of the rest of ACKS, there is virtually no historical evidence for the existence of “Indiana Jones”-style traps in the ancient or medieval world. So this is definitely being Made Up ™.

This is great. I have players hounding me to buy traps for their treasures…
I’ll post any feedback from play.

Duskreign’s Minion here.
Thank you Alex, this is great. Unfortunately this just doubled the cost of my hideout :slight_smile:

Very cool.
I wonder if you could generalize resetting by having these costs as the “manual reset” price (keep those henchmen busy!). An automatically resetting trap or adding a reset mechanism could be some multiple of the original cost (10x, maybe? 33x may be a bit much) and require the services of an engineer if it’s not part of a larger construction project.
Attack throw of dart/arrow trap may not be necessary if they just necessitate a saving throw vs. Blast & Breath (making them more of a spray of arrows/darts rather than a single shot). Having an attack throw makes sense from the standpoint of making armor useful, but if they’ve triggered the trap they’re presumably standing in exactly the wrong place already.
Magic is cheaper here for one-shot traps: Glyph of Warding has a base cost of 150 gp if you can find someone to cast it.
I imagine magic traps would be constructed as magic items and be priced accordingly (and again dependent on finding a caster). Might be useful to have an example or two of those. 1,500 gp for a one-shot Fireball trap, 15,000 for a Lightning trap that resets daily, 16,500 for a Magic Missile trap that resets every turn.

Great idea on the magic traps!

Question on the pit. Should it really be more costly to excavate a 10x10 hole than it is to excavate a 10x10 passage? Or do I misremember the cost of building a dungeon?

I assume that pit traps are fitted with a hinged opening that makes them appear normal until you walk on them and then perhaps fold back up after someone drops in so as to fool the next explorer - quite a bit of engineering really. Maybe they should be called “covered pit traps” or “concealed pit traps” to make this clear? A price for just an obvious sheer 10’ drop couldn’t hurt even if it is just restating what’s in the dungeon building section.

I had based the cost for the pit on this entry:
Corridor, dungeon (10’x10’x10’, hewn stone walls, flagstone floor) 500gp

Side effect of building magic traps as items: The precious materials used to improve the research throw seem likely to take the form of statues, inlaid gems, fancy carved reliefs, etc., which would explain why delvers keep running into magical trapped statues and gargoyles that spit flames rather than just getting zapped by an anonymous stone over the door.
I’ll have to break out my Grimtooth books and figure out some prices.

Nice idea, Undercrypt. In my section about generating dungeons I suggested that treasure placed in rooms with traps might be on corpses of those killed by the traps previously - but ‘in the form of material components for the magical elements of the trap’ is also a great answer, and serves the same function of both alerting players that there is danger here and also tempting them to mess with it anyway.

I like how you derived the costs Alex, but for my money (heh), there are issues in some of those base costs. Ii doesn’t, to my mind make any sense that a trap of falling bricks, for ex, is twice the gp of a portculis, given that a portculis is not exactly easy to make, whereas bricks falling from the cieling is probably dead easy to arrange.
Anyway most of those, going by the OD&D GP rates, look too expensive by half or so, and a couple others too cheap by half (plain earthen excavation and portuculis, scything blade). Might be worth looking at those base costs again to see if you think they really scale together.

Thanks for the feedback – I wasn’t aware there were rates for traps in OD&D. Do you have the prices handy?

No you’re right to think there are no trap rates, I’m refering to the OD&D construction costs as a base. So when you chop up a gatehouse into components, for ex, you get a base price of 1500 for the portcullis; Or 36 gp for excavating 10 * 10 section of earth, etc. But the thing isn’t the prices per se, it is the prices relative to each other. Maybe its the high expense of the shifting wall that’s causing it. Perhaps for the smaller/cruder traps there should be a lesser priced kind of “shifting wall” of the concealed trapdoor variety more in line with the cost of a secret door. I mean specifically, when I look at the price of an arrow or scything blade trap and a rolling rock trap I’d expect them to be pretty close not more than twice as much.