March 23, 2016

It's a Trap

Traps are one of the hardest things to get right in D&D, but there are a few different ways to use them in your campaign.

(Almost) Never Zap Trap

A zap trap is any trap that deals damage to a character but doesn't provide any real means of avoiding damage. For example, if the DM decides that a tile of floor will contain a spike trap that deals 6d6 piercing damage, with a Dexterity save for half, there is no definitive way of avoiding that damage short of announcing 'I check for traps' over and over. Most often, this is a terrible way of conducting traps.

Zap traps violate that all-important element, choice, and really only serve to provide frustration when you encounter them alone. There are times when the zap trap can be appropriate, typically as a punishment for a puzzle or an obstacle to be dealt with mid-combat, abreast of typical enemies. In fact, employing obstacles in combat is so important, it deserves its own article later on. The mere philosophy that a trap needs only a damage score and a location is the true flaw here; an effective trap requires a little more thought.

Someone Has to Live Here, You Know

If you are doing traps correctly, there should be a very blurry distinction between them and puzzles. This is because, ultimately, traps are not intended to be universal killing machines. The trap's designer, or whoever happens to occupy  the dungeon where the trap is laid, requires some means to disarm or bypass it, lest they become a hazard to him as well. There should always be a way around the trap. This is genuinely a story concern because it can absolutely kill immersion when your players, after being bombed for the dozenth time by zap traps, start asking "Who would ever set up these traps? No one can walk through this dungeon without being blown up!"

Make no mistake, this concern is also gameplay one. As a rule of thumb, your players should be able to out-think any challenge you throw at them, whether this is puzzles, social encounters, combat encounters, or traps. When your players feel like they have no options except to take damage from your traps, you've completely destroyed the illusion of choice and replaced it with learned helplessness. It's a terrible place to put your players.

Puzzles as Traps

To optimize for player choice and make your traps believable, their structure should be very similar to most puzzles: you present an obstacle that means the party harm or hindrance, the obstacle must contain several clues as to how it can be solved, and the players, through deduction, find one of the possible solutions. Be open to innovative solutions brought forth by your players, but know how the trap can be 'solved' before you present it.

Writing the best traps is a challenge of creativity, and placing yourself in the shoes of your players. I typically start writing traps by focusing on a mundane object with novel properties, and draw out my inspiration from there. For the example below, I'll choose a mirror, a favorite of trap-makers. Next, I construct a scenario around it that might involve a feasible physical trap or a completely magical effect. In this case, I'll use the obvious idea that a mirror can duplicate an image. Then I start to poke holes in my own, thinly-conceived device. Mirrors, for example, can't reflect things that don't leave images behind. So how does this come together?

A Practical Example: Hallway of Mirrors

A long hall lined with large, ornamental mirrors stretches out from the staircase down to this level of the dungeons. The mirrors are impressively bordered with gold and, though dozens of them line each side of the hall, only three on each side are angled to reflect a subject at a time. When a character walks down the hall and comes into the center of focus for the first six mirrors, his reflections turn to him, grinning and brandishing their weapons, striking him several times from all sides. A broken mirror releases a half-HP duplicate of the character that broke it -- destroying dozens of them is probably not an option.

By trial and error, with some deduction, players can notice that the mirrors don't attack if a character is invisible, but the mirrors also don't attack if the character in focus doesn't have a visible weapon (for the mirrors' images are formed without weapons themselves.) This presents the two most likely solutions: make the entire party invisible, or disarm them completely, storing all weapons in a bag of holding or similar location. Other solutions might be possible, like having a very weak NPC commoner smash the mirrors to make fighting duplicates rather easy indeed.

The Reverse Intuition Trap

Sometimes all you need to present a trap is to take the intuition your players might have and completely reverse it. These are my favorite types of traps, and I'm notorious with my players for using them. Always, they require lateral thinking and a healthy amount of second-guessing. Here's one example that I used in one of my campaigns, and how my players solved it:

A Practical Example: The Thief's Tamper-Proof Trap

The party is infiltrating a warehouse controlled by the Thieves' Guild in search of a nobleman held captive there. The place is on the edge of the docks and is eerily abandoned. Weapons at the ready, the party cautiously makes their way through the gaps of crates, watching for anyone that they might encounter. Then, the barbarian hears a loud click and feel the section of floor under his foot depress slightly. He freezes in place, and the rogue rushes to his aide, discovering a sophisticated explosive trap underfoot, apparently triggered by a pressure plate, much like a landmine. The DM rolls for the rogue's Dexterity check to disarm the device in secret, and it explodes.

This happens again, this time with the party fighter on the other side of the warehouse, and the rogue again rushes to disarm the device, this time expending inspiration to ensure a good check. It explodes again. The place is littered with the landmine devices and the rogue seems completely helpless to disarm them: they explode every time tries, in spite of her excellent stats. Moreover, she is running very low on HP as her failures mount.

Finally, the fighter, helmed by a somewhat impatient player, rushes forward, deciding that he could simply clear a path with his large pool of hit points. He hears a click underneath his foot. He keeps walking; nothing happens. The realization dawns on the party all at once: if stepped on, the bombs produced an intimidating audible click, but were only rigged to explode if someone tried to disarm them while the pressure plate was depressed. The thieves familiar with this warehouse simply knew not to worry about the clicking floor, safe in the knowledge that the bombs would be lethal to any unaware interlopers.

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  1. Thanks for another tidbit of advice. Really glad you guys are looking out for the other GM's. I'm currently working with traps in a mini dungeon and would like some advice, if that's not too much of a problem.
    The dungeon is extremely small, it's only a house, and it's crawling with baddies. So the trap is going to be placed and most likely triggered during extremely tense combat situations. It leads to somewhere important, and it's goal is to lock the players out of that area, whilst still attempting to eliminate a threat. The PC's are around level 6, possibly level 7 when the reach the encounter.
    Any thoughts?

    1. I'd be glad to lend some advice!

      So it sounds like you're looking for a variation of a door trap. Since you're planning on using it in combat, it should deal damage like a zap-trap and, if you're looking to make things claustrophobic, it can do area-denial damage (though this implementation will vary widely depending on whether or not you're doing combat on a grid.)

      So here's a general concept you can run with:

      Elemental Door Trap
      This door blocks the way to an important area and is emblazoned with four large symbols representing the elements. When the players approach, the door shoots a line of fire from the handle diagonally across the room. If this is encountered mid-combat, the players will simply have to deal with avoiding the predictable lines of fire which alternate between 3 simple firing directions every turn.

      If the door take cold damage (or is simply splashed with mundane water), it moves to a lightning ray, which must be countered with something physically made of stone, an ice trap, which must be countered with fire, and a jet of stones, which must be countered with lightning damage.

    2. Thanks for the advice! I think this can come in handy with the encounter.
      I have been flirting with the idea of two spell glyphs that triggered simultaneously, casting Fire wall and thunderwave, but they'd do too much damage, and over complicates things a bit too much.
      I do like the idea of the elemental door trap, but if a better one can be given if I give a more detailed description of the encounter, it'd be appreciated as well.
      The trap is laid on a trap door that leads to a cellar, in which you gain access through from the outside of the house. Problem is, there's a set of walls that rings the grounds of the area, so the players have to enter those first. Not to mention it's guarded by a few baddies. So either a good rogue or a better distraction would probably deal with this encounter best. Problem is, the party lacks a rogue.
      Again, if you can help I'd really appreciate it, because I want to make this encounter as enjoyable as possible, seeing as it's the first real encounter that obviously revolves around the main plot.

  2. I'd like to add something about zap traps.

    From a logical perspective, what dungeon designer would fill their place with random pitfalls? Usually, a treasure vault, secret hideout, etc. needs to be accessible by its owner(s). Therefore, even in a dungeon that is entirely filled with uninspired zap traps, there HAS to be some rhyme or reason about it so its occupants don't trip anything themselves. So traps should follow patterns on the floor, have a hidden switch or pass phrase to disarm them, or be otherwise easy to avoid for those who know how.

    On a different note, never make a trap save-for-half. Whenever I stick a zap trap anywhere, it's always one of two things. Either it's a save for no damage (in the case of pitfalls, tripwires, or other stationary traps), or the trap makes an attack roll against the character's AC (in the case of arrow slits, spell traps, or other projectile devices). The traps should be very forgiving and low-damage at first, unless somebody's a moron.

    I had this one trap in a 40 foot hallway that shot projectiles of increasing size from the walls every 5 feet. My party was cocky after having solved the last couple puzzles, and their barbarian, a half dragon named Argax (God, do we have stories about him), decided to tank the damage after being hit with the first needle. He told me he was gonna run the whole thing in hopes of dodging as many as possible. I ruled that if he runs, it would take him half his movement speed to stop. He said ok. The first few were needles, then darts, then crossbow bolts, then javelins, and finally, the last pressure plate threw a ballista bolt at him. Needless to say, the party wasted a good chunk of their healing supplies getting him back up.

    This is a zap trap, yes. But it only punishes players if they're dumb, and makes for a pretty funny story afterward.

    1. Come to think of it, I'm pretty sure the ballista bolt was the second-to-last trap. The last one threw a live mountain lion or something like that at him.

  3. Great article, but I have to disagree that there isn't a place for "zap traps". Not every encounter needs to be novel, and this applies to traps as well. Not every trap will be a puzzle. Sometimes, you want to stick with the classics: you step on a pressure plate, you fall into a pit onto some spikes; Open a chest, a needle pricks your hand and poisons you; etc. I mean, you say "What dungeon designer would fill their dungeon with random pit traps?". Well, what dungeon designer would spend thousands of gold pieces on intricate puzzle-traps when a simple Explosive Runes would do?

    On that note, most traps with a magical detection trigger are set to only trigger when a person not exempt by the spell passes by. So a dungeon designer could set his trap to only affect non-evil characters, or only affect peoples besides evil goblinoids and himself.

    1. Well, your mileage will vary, but the point I intended to get across about zap traps is that they, by design, take away from player agency. You can use them in effective ways, but if your players are only acted on by traps, not acting on them, you're doing it wrong.

      The DMG approach to traps for a long time has been just listing stats, which tends to mislead new Dungeon Masters into thinking that traps are more of a mechanical contrivance, rather than a part of the world, which is completely backwards. It's easy to find solutions (normally magical ones) that make a dungeon impenetrable to all but the dungeon designer, but it's easy to craft story reasons why it wouldn't be, and this is far more palletable to the players because it makes their experience of the game better. Ultimately, that's all that matters.