Magical traps, just how exploitable are they?

[EisenKreutzer]

I see a lot of mentions of traps, and it's almost never in the context of an actual trap like you would find in a dungeon.

It seems trap has become a sort of shorthand for a magical effect built using the vague trap-creation rules of 3.5 that neither behaves or is intended to be an actual trap.

So, what exactly are the rules for creating magical traps, and in what ways can these rules be bent or interpreted to produce the effects people are talking about?

[Galen]

http://www.d20srd.org/srd/traps.htm#magicDeviceTrapCost

An automatic-reset trap using a 1st level spell at caster level 1 costs 500 gp and 40 XP.
Now, get a small box and put an automatically-resetting Cure Light Wounds trap on the lid. There you go, unlimited healing for the entire party, just keep reopening and closing the lid. And it costs actually less than a Wand of Cure Light Wounds would.

And that's probably one of the least abusable trap uses.

Edit: there's actually no need to bend any rules, it's all quite straightforward by RAW.

[EisenKreutzer]

I'd say that since the rules were intended to be used for building actual traps, and not as a system for hanging conditional, self-rearming spell effects, it's bending the rules atleast a little.

But you are technically correct, the rules as written do allow these kinds of shennanigans.

So, we've seen the box of unlimited healing. What are some of the really big ones?

[Thanatosia]

I'd say that since the rules were intended to be used for building actual traps, and not as a system for hanging conditional, self-rearming spell effects, it's bending the rules atleast a little.

But you are technically correct, the rules as written do allow these kinds of shennanigans.

So, we've seen the box of unlimited healing. What are some of the really big ones?
Well, Create food & water on a rearming trap is a big part of what makes the trippyverse so trippy as I understand it, as you've essentially negated the need for any actual agriculture, land, farming, supply lines, etc to feed a population, and very cost-effectively to boot.

[1pwny]

I'm pretty sure that generally the populace reffers to Wish traps, which can be easily bought with late-game WBL. And once you have a single, reusable Wish trap, you have infinite money and can do whatever you want.

Or at least, that's how I think it goes. :smallbiggrin:

[Vortenger]

All of those things are true, but what makes the Tippyverse Tippy in the first place are Circles of Teleportation linking major towns, obviating the need for travel time. The resetting traps of create food/water, cure disease, bestow curse: inability to reproduce, and its inverse, are secondary and create the rest of the post scarcity society.

/thread derail

The spell that creates ambrosia for free xp on crafting is pretty awesome.

[Curmudgeon]

So, what exactly are the rules for creating magical traps, and in what ways can these rules be bent or interpreted to produce the effects people are talking about?
Here's the essence of it, from Dungeon Master's Guide page 74:
PC-Designed Magic Traps: If a player character wants to design and construct a magic trap, he must have the Craft Wondrous Item feat. In addition, he must be able to cast the spell or spells that the trap requires—or, failing that, he must be able to hire an NPC to cast the spells for him (see NPC Spellcasting, page 107). When you and the player have agreed on what spells and other elements the trap contains, you can determine the cost of the raw materials for the trap and the CR of the trap. If the DM doesn't agree on any element of such a custom trap, there is absolutely no exploitability. When I'm DMing I simply disagree with any non-damaging custom trap plans, and they don't get created.

[Urpriest]

Here's the essence of it, from Dungeon Master's Guide page 74: If the DM doesn't agree on any element of such a custom trap, there is absolutely no exploitability. When I'm DMing I simply disagree with any non-damaging custom trap plans, and they don't get created.

I see where you're going, in that this is kind of like custom magic items. Both need DM approval, which gets rid of the really stupid stuff.

But there's a very important difference: custom magic items explicitly advise the DM to balance them based on other items. This means that the DM has a good idea of what is and is not appropriate, provided they take the time to research existing magic items.

With traps, the situation is less clear. It's not at all obvious that traps should be balanced against magic items, in fact several traps are rather dramatically better than comparable magic items (Spell Turrets, for example). Picking on the Trap of Cure Light Wounds specifically here, you can't even argue it's unbalanced as a source of healing, as other sources of healing in the game have wildly divergent power with no relation to price (healing potions vs. wand of lesser vigor vs. healing belts vs. DMM Persist Mass Lesser Vigor etc.)

As people immersed in online D&D culture, we know that beneficial traps can rapidly go out of hand. But what tells a DM without that experience which trap configurations are unbalanced? What criteria should be used?

[Cruiser1]

As people immersed in online D&D culture, we know that beneficial traps can rapidly go out of hand. But what tells a DM without that experience which trap configurations are unbalanced? What criteria should be used?
Any auto-resetting trap targetting an individual or area must be an attack, i.e. something that if cast by a PC would bring down invisibility. Any other spell in a trap must be single use. (For example, a Wall of Stone trap to seal off the way adventurers entered the room, which only needs to be single use anyway.)

Also, traps must be stationary and anchored within a 5 foot cube area of solid ground. If the trap space is ever dug up or disconnected from the ground, it's permanently dispelled as if disjuncted. That means no traps on moving objects like a ship or carriage, and definitely no traps inside a bag of holding or on your person. (If you want spell effects on your person, use Craft Contingent Spell.)

[awa]

Any auto-resetting trap targetting an individual or area must be an attack, i.e. something that if cast by a PC would bring down invisibility. Any other spell in a trap must be single use. (For example, a Wall of Stone trap to seal off the way adventurers entered the room, which only needs to be single use anyway.)

Also, traps must be stationary and anchored within a 5 foot cube area of solid ground. If the trap space is ever dug up or disconnected from the ground, it's permanently dispelled as if disjuncted. That means no traps on moving objects like a ship or carriage, and definitely no traps inside a bag of holding or on your person. (If you want spell effects on your person, use Craft Contingent Spell.)

so no trapped doors or chests?

[Rubik]

I'm pretty sure that generally the populace reffers to Wish traps, which can be easily bought with late-game WBL. And once you have a single, reusable resetting Wish trap, you have infinite money and can do whatever you want.

Or at least, that's how I think it goes. :smallbiggrin:Consider nabbing yourself either a djinn or a zodar and using its (Su) Wish to create a resetting Wish trap that turns a molecule of O2 into a resetting Wish trap that then immediately Teleports to a random location and turns a molecule of O2 into a resetting Wish trap that then immediately Teleports to a random location and turns a molecule of O2 into a resetting Wish trap that then immediately Teleports to a random location and turns a molecule of O2 into a resetting Wish trap that then immediately Teleports to a random location and turns a molecule of O2 into a resetting Wish trap that then immediately Teleports to a random location and turns a molecule of O2 into a resetting Wish trap that then immediately Teleports to a random location and turns a molecule of O2 into a resetting Wish trap that then immediately Teleports to a random location and turns a molecule of O2 into a resetting Wish trap that then immediately Teleports to a random location and turns a molecule of O2 into a resetting Wish trap that then casts Mass Heal, followed by a Reach Spell'd Chained Spell'd Regenerate.

It'd kill every undead on the Material Plane within the day, and wipe out everything from disease to any kind of disability (including deafness, blindness, and paralysis). And all for the cost of a single Planar Binding.

If you wanted to wipe out, say, the Evil alignment, you could do something similar with either Mindrape or Sanctify the Wicked.


Any auto-resetting trap targetting an individual or area must be an attack, i.e. something that if cast by a PC would bring down invisibility. Any other spell in a trap must be single use. (For example, a Wall of Stone trap to seal off the way adventurers entered the room, which only needs to be single use anyway.)A necropolitan can still utilize Harm in a trap, as could a living creature with Heal (since it damages undead).

In fact, there are lots of spells that could fit the bill here, considering that there are ways to use plenty of spells in ways they (supposedly) weren't designed for.

[Jowgen]

Lots of trap stuff popping up these days...

One good by the books limiter for trap shenanigans, much in line with the above-mentioned "must be unmoving" houserule, comes from Stronghold builder's guidebook. It's rules for Wonderous Architecture equate said wonderous architecture to traps, allowing Disable Device on them and even having the same pricing equation for completely stationary wonderous architecture. It is quite easy to extend the written limitations on what can and can not be Wonderous Architecture to traps; providing a good baseline for limiting them. :smallsmile:

[Kelb_Panthera]

The answer to this issue is, imho, in the stronghold builders' guidebook.

The guidelines listed under magical architecture describe costs that map very plainly with both the dmg's rules for magic item creation and its rules for magic trap creation, based on the mobility of a magical object.

The single noteworthy difference between the two formulae is the constant value: 2000 for items, 500 for traps. It so happens that these are also the constants that SBG gives for the most and least mobile magical effects, respectively.

While it's not RAW, it's logical and reasonably well balanced to impose these guidelines universally. Trap in the floor of a dungeon; 500gp constant, trap in a wagon; 1000gp constant, trap in a locket; 2000gp constant.