In a tabletop game, "traditional" mechanical traps are awkward to include in a dungeon, and that is a real shame. I commented briefly on the problem of traps in my post on module construction, but now I want to dig into that topic more deeply and propose a new solution (or at least a new tool for addressing the matter; it isn't a single-solution kind of issue).
Up through 3e, traps remain consistent in their general form*: something for the rogue to do. With a few exceptions, the only thing other classes can do is suck up the damage, since they have no particular chance to even spot the trap. (A special exception goes to those earliest editions of D&D that had no rogue or thief class.) Anyway, traps consistently represent a lot of dice-rolling by the rogue while the rest of the team sits on their hands. On the other hand, in some editions the thief is such an undesirable class that this is just about all they have going for them. 3.x completely changes this - as long as you're not fighting things that are immune to Sneak Attack, the rogue is a wonderful class with a lot of interesting options.
Still, 3.x retains the ham-fisted approach to niche protection, making it impossible for any other class (no matter how hard they try) to equal the rogue's trapfinding and trap-avoiding abilities. Trap design could not do a lot more to exclude other classes. The next problem is that, even for the rogue, it isn't all that engaging - there's a skill roll or two, and failing any of these rolls results in harm or death. The apparent decision points are whether to advance slowly enough to check each square thoroughly, and whether to disarm traps or just bypass them (usually with varying degrees of difficulty).
Let me break this approach down just a tiny bit more. Given the setup, what's really going on is that rogues provide the party with an extra layer of saving throws against the trap. If the first saving throw (detection) is successful but the second one (disarmament) isn't, the rogue takes the damage instead of someone else, or everyone else, doing so. Like all saving throws, there aren't a lot of choices to make; unlike other saving throws, the player is expected to alter her approach to gameplay in order to be allowed the "detection saving throw."
There's a countervailing point to this criticism of trap mechanics: they're designed based on feel, nominally imitating mechanisms that make sense for the dungeon's residents to have installed, both tactically and technologically. Tripwires, pits, pressure plates, trapped locks (and locks themselves, for that matter) and so on, are relatively simple and easy to understand. I'll be coming back to this point.
*Especially in the 1e era, another approach to traps also appears, in the works of the incomparable and bizarre Grimtooth, by Flying Buffalo. Grimtooth's traps are famously elaborate, ridiculous, and unfair - the latter of which may be a reasonable tactical decision for the defenders, but is a terrible gameplay decision on the GM's part. Still, convoluted traps that endanger the whole party are not all bad - everyone is invested in and able to contribute to finding a solution. In Grimtooth's works, the insane deathtraps are often obscure, guess-what-I'm-thinking physics challenges. I hesitate to call them puzzles, on the principle that puzzles have clues. They fit tolerably well into funhouse dungeons, but most of them would feel out-of-place in a dungeon more focused on verisimilitude.
Then there are glyphsand symbols. Rogues can theoretically do something about these, but it's a lot easier for level-appropriate spellcasters. Glyphs enter play when other kinds of traps are still relevant, while symbols make their first appearance in 5th-level spells, and keep improving up to 8th-level spells, long past the time that the hardest traps in the game are trivial for a rogue who has put any points into traps skills. My point here is that magic completely replaces mechanisms, and 3.x glyphs and symbols can combine with a normal encounter, or they can be an encounter. (Ahem, greater glyph of warding, spell: with summon monster VI, this becomes a single creature of CR 5-7. Maybe a little low for PCs going up against a caster of level 11+, but as a way to delay and raise an alarm, it's not too shabby.)
4e took a drastically different approach to traps (and hazards; for simplicity I'll use "traps" to cover hazards as well). Recognizing that the 3.x approach to traps generally entertained only one player, and didn't offer that player particularly interesting choices, 4e brought traps more in line with monster design (including giving them "creature" types) and linked them directly to encounters. That is, players really only encounter traps in connection with monsters. Also, dealing with traps very often requires the skills of other party members: Athletics, Dungeoneering, attack rolls, and Nature. Around 16th level, Arcana and Religion suddenly replace all of those as the useful skill of record. This follows "high level = high magic" well, but it's a bad mistake in terms of game support for all of those other skills. The bounded accuracy of D&D Next pays off well here in redeeming this error - those low-level traps could still be a hindrance, if not a threat, and thus the skills to thwart them retain this more interesting application.
The other problem with 4e traps is that once players discover them, the trap is as much or more of a problem for the monsters as it is for the PCs. Some traps solve for this problem, such as the Altar of Zealotry (and I love the idea of a PC tearing an unholy symbol off of an enemy's neck so that the Altar targets that enemy as well); in other cases, the enemies may just have the benefit of knowing which squares the trap targets, and thus the trap pairs exceptionally well with monsters that have forced movement or immobilizing effects. (Beware the line between "challenge" and "frustration." If you know an infallible way to find that line, for God's sake, sell your knowledge to me, and together we will rule this galaxy industry.) Also, there are a tiny handful of traps that are a whole encounter unto themselves - that is, they are statted as Solos.
There is a lot to like about 4e trap design. The traps are evocative, they include multiple characters, the information presentation is probably about as good as could be asked, there aren't a ton of obscure +2/-2 modifiers, and if you're good at encounter design, you'll probably manage a few casualties. On the other hand, more-or-less requiring creatures in order to use traps well runs counter to the fiction, and undermines the non-combat challenge that traps represent. 4e wants the GM to parse a trapped treasure chest as a skill challenge, emphasizing all of the problems in skill challenge design where only one character in the party has the applicable skill. So like everything else in 4e, the designers made a bold but imperfect step forward, and because it was both imperfect and unfamiliar, it has been largely abandoned as a design model.
4e's DMG 2 - a book I have praised before, at length - includes more than two pages on trap theory (starting on p. 64, and with excellent sidebars on pp. 65 and 70) that should be required reading for all dungeon-using GMs everywhere. There are valid reasons to discard some of this advice, but it's good enough that you need to examine your plans carefully first.
I mentioned that 3.x traps involve no real decision points, and 4e does address that. Most traps have countermeasures as well as direct means of disarmament. Most countermeasures are a sample list of odd things players might want to try to protect themselves or destroy the trap through main force. This is definitely a good thing to include, and in a lot of cases these options appeal to non-rogues, but if there's a whole encounter involved, presumably everyone else has something useful to do already.
So I've talked about the development of traps in the tabletop D&D environment. (I assume other systems, especially GURPS, have put some amount of design effort into traps, but I don't know anything about it.) My other experience of a trap-rich environment is LARPing, where a well-built traps module is hailed as a thing of beauty. From the very simplest of devices, LARPs derive intense, even harrowing gameplay, so I'm going to talk about that for a bit because if a prodigious wordcount is good enough for Haran Roeh it is good enough for me, baby.
Anyway, most LARP traps take the form of a length of fishing line, some duct tape, and a mousetrap. Pull the line, trip the trap, suffer the effect. There are a small number of other devices - hazards, mainly, like Rotating Blades of Death tee-em - but most of what goes on is some new trick with the three basic materials. Notably, the counter-weight trap: clip the line and you're all done. The sticky trap: watch where you step, because the line is lying loose on the ground with an up-turned adhesive. Pressure plates are not unknown, but they're tough to do well. Also, doors are the worst, because that's the points where it's easiest to affix lines and the trapper has the narrowest field of vision.
Now, there are a lot of things in this that I can't see how you'd ever re-create in a tabletop game. A Search check is painfully unsatisfying, compared to the experience and dread of finding whatever you find. With each individual trap being so simple in execution (apologies to the hard-working marshals who take hours to lay all that line), finding one trap is generally a sign that there are more. The lighting options available to heroes in tabletop games are quite verboten (for safety reasons) in LARPing - and let me tell you, a few glowsticks or candles does not add up to "well-lit" the way a torch or hooded lantern does in D&D. (This isn't about how one medium of gaming is better than the other on the whole - LARPing just does this one thing that I like better than the tabletop medium does.)
How about party inclusion? That must be admitted as an area in which LARP traps often leave something to be desired, except that a module party's roster isn't determined until the actual start of the adventure - if players know they're getting into a trap-rich environment, they don't bring a bunch of thugs and the like. They bring a couple of traps rogues, a healer, and maybe one brute. If the healer and the brute stay outside and chat (or play cards, or whatever) while the trappers go to work, that's what they signed up for, and they aren't risking talking over the GM the way they would be in a tabletop game. The general statement holds that five or ten minutes of patience is less frustrating in a LARP than a comparable 10-20 rounds of being passed over in a tabletop game. As much as anything, I think this is because even when you're not doing anything in a LARP, you experience in-character tension of the unknown; this seldom if ever comes across in tabletop play.
Enough With the History, How About an Idea?
I'd like to explore a model that splits the difference between these and draws on the strengths of all of them. In addition to some use of Rube-Goldberg-like puzzle or deathtrap rooms (often hard to justify, but usually a lot of fun), I'd like to see trap encounters that use smaller elements in combination, keeping mechanical traps on the table for as long as possible, and arranged so that the rogue needs the help of one other party member.
My theory here is that everyone stays involved if the rogue and one other party member resolve the problem, as long as everyone else feels that the next trap encounter might give them a chance to shine (and as long as they're reasonably likely to be right). The rogue is an active party in each of these cases, so the trap concepts below are identified by the other character taking part in the action. Most of these are well-modeled in 4e's rules, save that their striation by level means that classes drop in and drop out of trap gameplay for whole tiers of play.
To handle this within 4e's framework, the simple solution is to scale up the traps that Athletics (we'll sum that up as "warriors") and Nature/Dungeoneering ("treehuggers") help with, and scale down some of the high-end Religion ("healer") and Arcana (...arcane) traps. Thus:
I'm not sure why WotC's designers stop using good old iron and steel for their traps, except that mechanical traps are low-magic. Anyway, the Armor table over in the Player's Handbook suggests high-end materials that could be fun as a means of justifying whirling blades that cleave through high-level armor, and carry suitably hideous damage expressions. In 4e's context, it's a mistake to stress about why the DCs for Perception and Thievery checks for strictly mechanical traps scale up as they do, while in a 3.x or D&D Next context, that scaling doesn't occur. Also, it's fine to keep using pressure plates and tripwires as triggers in high-level play - places you either can't stand or can't move through are still interesting constraints even when flight and teleportation become common movement modes. Just, you know, hang the tripwire higher.
These are a little bit harder to justify. I mean, when you're powerful enough, do we want environmental conditions that are recognizable from earth to threaten you? But you know, lava never gets old as the basis for traps. Seriously, "the floor is lava"? Awesome when you're six, awesome when you're sixty-six. 4e doesn't have a Planar Knowledge skill, so traps (especially hazards) that are natural conditions of the Outer Planes are pretty great for this. If you thought a Treacherous Ice Sheet (level 5 obstacle) was bad news, maybe try a jagged fragment of a dead god of winter on (or from) the Astral Plane. (If this is too gonzo for you, epic-tier 4e may not be your bag. There's nothing wrong with that.) On the same principle, consider adding Nature as a valid skill option for the Field of Everflame.
It's too easy to let healers interact only with the aftermath of traps, reducing them yet again to first-aid kits on legs. This is something I've railed against in other contexts, so I'm not letting it go this time either. I think it's excellent that Religion features in high-end traps, but there is no reason at all that there can't be a less-ruinous Word of Power to create a lower-level Symbol of Suffering (level 24 warder), or a less-defiled location for a weaker Altar of Zealotry (level 15 lurker). Beyond this, I'd be interested in giving healing spellcasters the ability to suppress the toxicity of a poison already in evidence. This would spend their action for the turn to reduce or eliminate the poison damage of a particular attack or trap, for a duration (3.x) or Save Ends (4e) or Concentration (D&D Next). Healer traps, then, are the ones that are coated in contact poisons when the rogue must not be hindered by thick gloves, or surrounded by a fog of poison gas when there is no wind to clear it away. Also, I just think that giving healers a chance to partially tank fights with green dragons, giant scorpions, and so on could be super cool.
Maybe you're thinking, "Delay poison and neutralize poison already cover this functionality, thanks." To this I say, do yourself a favor and change these spells to something that doesn't confer immunity or require touch-range usage. Short range will do just fine.
I can't help but feel like these design themselves. If low-level means low-magic, then go for low magic - hedge magic, that is. Don't disturb this arrangement of runesticks, or face the Curse of Excessive Arachnids. One could do a damn sight worse than reskinning the Doomspore (level 3 obstacle) to cover that idea. Don't trespass across that circle of iron and salt until the rogue and the wizard finish unraveling the magic, or you'll have to fight the djinni that hides within. (Also, it's okay to bulk up Healer traps with "arcane traps" that have been flipped over to use divine magic.) If Whirling Blades are good (they are), Fiery Whirling Blades should be great too.
Honestly, the problem with arcane traps is that it's too easy to go to magic as an explanation, thus over-valuing Arcana as a skill. This is a recurring problem in 4e, though, and I think it would help a lot if Arcana very rarely accomplished tasks in itself, but more often provided some directions on how to accomplish goals using other tools - such as hedge magic to counter hedge magic.
So I have not exactly blown your mind with these ideas, but maybe I've rearranged things just a bit. I plan to experiment with the idea that traps are a two-person effort, where the second person varies from one encounter to the next. The rogue still gets to shine, but shares the spotlight. I would love to hear more trap concepts, especially things that expanded on high-end Warrior traps and low-end Healer traps.