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Unearthed Arcana Unearthed Arcana: Traps Revisited

Actually an interesting article. I'm still scanning through it, though. I like the way they discuss the traps, their creation, and countermeasures (something that was missing, I think, from the DMG). Poisoned Tempest is an absolutely inspired and devious trap! I love it!!!

Actually an interesting article. I'm still scanning through it, though. I like the way they discuss the traps, their creation, and countermeasures (something that was missing, I think, from the DMG).

Poisoned Tempest is an absolutely inspired and devious trap! I love it!!!


I don't have a problem with a player saying "I disarm the trap." (I often play with new or unimaginative players). I consider it MY job to say "okay, you pull out a wooden shim and a little hammer (from your thieves' tools) and gently tap away until the pressure plate is secure." or whatever to inspire them in the future.

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Lowcountry Low Roller
4) While passive perception should be the default to spot a trap, Investigation might well be used when a player says, "I am curious about this desk. I will carefully examine it for traps." Indeed, the difference in Countermeasure descriptions for the Falling Gate trap and the Fiery Blast trap give me the impression the author isn't sure how to differentiate between Investigation and Perception sometimes - both traps use a pressure plate, so why include Perception to spot one and Investigation to spot the other when that portion is essentially identical? I think more traps should include entries for both in the Countermeasures section.

Good point. Passive perception to notice traps embedded in the environment designed to arrest your movement. Active perception or investigation to find traps within a particular object designed to kill you or destroy said object.


Lowcountry Low Roller
It also occurs to me that environment traps need to get triggered for them to be interesting to the players. As others have noted, spotting a trap and going around it is pretty dull. What's exciting for the players is getting caught in a trap and having to overcome it. With the canvas covered pit trap, a player steps onto it and feels the "ground" give way beneath their feet... "What do you do?" - that's fun and interesting.

Only environment traps that cannot be circumvented should be detectable IMHO. I.e. sure you've found the trap but you can't just go around it. You now need to figure out how to safely get past it. The classic step on just these flag stones to successfully get across, for example - one false step and it's triggered.


I am now picturing kobolds who lay down random canvasses in their layers... who hide in the shadows and try to push those who investigate the canvass into the pit... who stand at the edge of the canvass and use missile weapons...or who lay down canvasses that have dart traps attached when you pull them up...

or something like from Tomb of Horrors where there are fake pit traps next to pit traps to discourage the "i jump over it" solution. yes, you see a pit trap, but without the investigation, you don't know that it is fake, and miss the one on the other side of it


I would totally use the simple pit trap as part of a complex trap.

Adventurers: "Yeah, that piece of canvas isn't too obvious is it? We skirt the edge of the pit and get to the other side."
Me: "OK, great. That's easy enough, however when you get about three quarter's of the way past the pit you hear a sickening click as the person in the lead steps on a pressure plate. An instant later the corridor wall next to the pit slams inward, knocking you off the ledge and into the pit."

Add a relatively high Passive Perception check for the pressure plate, unless someone stated they were investigating the ledge. Also a Dex save to avoid getting hit by the wall and knocking you into the pit. I would give bludgeoning damage for the wall and for the fall.



I completely see your point @pming, and I agree with you on the simple traps being speed bumps.

But what about the complex traps, if anything, doesn't work for your style? I think those are more than a resource drain, much like placing a mummy in a temple is more than a resource drain.

Genuinely curious, since to my eye those complex traps are made for more killer/narrative DMs

I think it's the end result that bothers me. They all seem intent on primarily being a HP/Healing drain, with some adding in a Movement hindrance. That's great and all...but, er, "simplistic"? Common? Typical? Not sure what word to use. Now don't get me wrong. Damage is a good thing for traps to do, but for the more "Deadly" ones, I want them to be, well, "Deadly". I want a Poison Gas trap under "Deadly" to be something like "Con sv., DC 15; Failure = Death; Success = 1d8 hp per round for 10 rounds or until removed/neutralized". To me THAT is "Deadly"...it will kill you if you fail, and may kill you anyway if you succeed. I want a rolling rock trap to be "A 10-tonne sphere rolls down the hall; Dex sv., DC 15 to avoid for M, DC 10 for S, DC 20 for L; Failure = Death and most items on character destroyed".

Death is Death...doesn't matter if you are 2nd level, or 20th. By linking traps primarily to HP's, it does a HUGE disservice to the origins of the game, IMHO. Yes, I'm an "Old Skool" DM (obviously), and that's how we play the game (and most RPG's we play, TBH). If a player describes what he does to nullify a poison needle trap, and it seems plausible, then thats that...no rolls needed. If he describes what he does that seems possible, but has some chance for failure...then roll. In short, the PLAYERS choices/descriptions have more of an impact than the stats on his sheet, usually, with regards to most aspects of any game I'm running.

Anyway, i still think it's a decent stab at it for young, new, or "D&D Lite" gamers. But for a more...hmmm.... "Hackmaster-Style" group they kinda fall a bit flat.

PS: For those talking about "Perception" use for detecting traps....I just outright tell them "It's a trap". Depending on how well they rolled they will get more info: "It's some kind of large, floor based trap"..."It's some kind of large trap in the floor or on the low sides of the walls"..."It's a spear trap that shoots spears out from the sides of the hall at about 1' height". After that, it's up to the PLAYERS to tell me how they go about discovering just how it works and all the details (with an Investigation roll). PLAYER ideas trump dice rolls, however.


Paul L. Ming
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Developing my thoughts in post 22 and post 43, I think a good approach to traps would begin with a thorough treatment of triggers explaining how Perception/Investigation checks work with that trigger, what thieves' tools can be used for with that trigger, etc.

[SECTION]Why is describing triggers in more detail important? Think of my approach like the introduction to the Monster Manual. There's a section on "What is a Monster?", "Where Do Monsters Dwell?", explanation of monster types, explanation of a stat block. The UA article is kinda moving in that direction, but needs to go further. A trigger is the primary mechanism by which a character first interacts with a trap, and there really aren't that many triggers presented between the DMG and UA article, just 6 actually. Establishing a common mechanic/approach to each trigger (the same way 5e tries to do with similar spells) would go along way toward clearing up confusion about how traps work.[/SECTION]

Here's my take on the 6 common trap triggers that appear in the UA article and DMG (though I think there should be more)...

False Floors
Magical Wards
Pressure Plates
Spring Mechanisms

Trigger Types

False Floor
A false floor is a brittle or fragile section of floor, typically designed to conceal some variety of pit trap. It gives way when a certain amount of weight is placed on it (usually ~50 lbs).
Trap Examples: pit trap, spiked pit trap, gelatinous cub pit trap, acid pit trap, etc.
Notice: Most of the time, a false floor is undetectable. Wisdom (Perception) checks can detect signs of weathering where monsters skirt the false floor or periodically replace it, but will not identify the false floor itself. The exception to this is that a dwarf will automatically recognize the change in stonework used for a false floor built into stone.
Saving Throw: When a character triggers a false floor, they must make a DC 15 Dexterity saving throw as it crumbles away beneath them. On a failed save, the character falls into whatever trap awaits below the floor. On a successful save, the character can use a Reaction to grip the edge of what is now a hole, though this requires two free hands (i.e. dropping anything they were holding, which falls down the hole).
Disarm: Interpretting the signs of a false floor and skirting around it is the best defense, as is flying or levitating. Alternately, a false floor can be triggered with a sufficiently heavy object or a long plank can be laid across it allowing safe passage.
Encounter Design: False floors can be dangerous when used with particularly threatening pit trap, but their real danger comes from their ability to split the party. Additionally the threat posed by a false floor is magnified when encountered with monsters that Shove or otherwise inflict forced movement (e.g. minotaurs) or spells and effects that inflict forced movement (e.g. gust of wind). False floors are a great way to use a trap to tell a story, opening up a heretofor unexplored area of a dungeon.

A lever is a trigger that is deliberately pulled by monsters (or unwitting characters) to activate a trap. This includes winches, pulley systems, or any other mechanism that requires an action be taken to activate.
Trap Examples: falling gate, false doorknob, scything blades
Notice: Generally, a lever’s presence will be obvious, requiring no check to notice. However, sometimes a lever will be placed in a recessed alcove that is designed so it’s not visible until either in bright light or within 30 feet of a character with darkvision. Other times a lever will be disguised as something else, such as a doorknob, rung of a ladder, or even a book on a shelf.
Disarm: A lever can be switched off as an action. It can also be jammed with a piece of equipment such as a crowbar or dagger preventing it from being pulled. While thieves’ tools aren’t much help with disarming a lever, they can be used – given at least 5 minutes – to swap the on and off positions of the lever.
Encounter Design: A lever is usually placed in a place that’s hard for character to reach, but easy for monsters. Getting within 30 feet of the lever (mage hand range) should usually be a challenge. Sometimes, however, a disguised lever will be placed in plain view.

Magical Ward
A magical ward, like the glyph of warding spell, is a form of abjuration which triggers according to specifications defined by the spellcaster.
Trap Examples: any use of glyph of warding, fire-breathing statues, sphere of annihilation
Notice: A magical ward is almost invisible to the senses, though an Intelligence (Arcana or Investigation) check made as part of a thorough search – typically requiring at least 5 minutes – will discover barely perceptible glowing runes. If this check is made in pitch darkness it has advantage. Detect magic will always detect a magical ward as abjuration magic.
Disarm: Dispel magic cast at the appropriate level will disarm the magical ward. Depending on the individual ward, other means of disarming may be possible, such as dealing cold damage to a ward triggering a spell dealing fire damage. Thieves’ tools can’t disarm a magical ward.
Encounter Design: When used in moderation, magical wards can go a long way toward evoking a dungeon’s theme. It’s worthwhile to think of unique ways that characters can become aware of the trigger without detect magic and overcome it without resorting to dispel magic. If there’s a password or object to bypass the ward, consider which creatures in the dungeon know the password or possess such an object.

Pressure Plate
A pressure plate is a section of floor masked to look indistinguishable from the rest of the floor, that when a certain amount of weight is placed onto it (often about 50 pounds), and then removed from it, triggers a trap.
Trap Examples: falling gate, poison darts, rolling sphere
Notice: A well-designed pressure plate is usually not noticed until it is triggered, when a character feels it drop about an inch beneath them with a soft “click” sound. Causing structural damage, however, such as a thunderwave spell or a ring of blasting, will cause a pressure plate to vibrate. Additionally, a character with tremorsense can detect the presence of a pressure plate with a DC 20 Wisdom (Perception) check, due to subtle fluctuations of the plate in response to creatures moving across the floor.
Disarm: The easiest way to handle a pressure plate is to find a suitably heavy object to weigh it down, thereby freeing a creature to step off of the plate safely. However, tearing out nearby flagstones – requiring at least 5 minutes – allows a character using thieves’ tools (or ball bearings) to prop up the plate so that it cannot be depressed anymore.
Encounter Design: A pressure plate presents a dilemma for characters to resolve, and thus it’s best placed in an area that will either feature some other external pressures (e.g. monsters or another trap) or in an area that the characters will repeatedly pass through (e.g. a “junction room” in a dungeon). Small humanoids may design pressure plates which have a weight threshold allowing Small creatures to pass over without triggering.

Spring Mechanism
A spring mechanism involves a tightly coiled spring, typically tiny and well hidden, that triggers when a trapped object is opened or physically manipulated.
Trap Examples: bear trap, bladed puzzle box, poison needle
Notice: In most cases, a spring mechanism is unnoticeable to the eye. Only a thorough examination of a trapped object – requiring at least 5 minutes and bright light – allows a character to make an Intelligence (Investigation) check to notice the glint of the spring mechanism inside the object.
Disarm: Simply avoiding the trapped object is the best defense, while thieves’ tools are the ideal way to disarm a spring mechanism. Lacking thieves’ tools, a character can attempt to break the object with an attack (referring to the damaging objects rule in the DMG), though if an attack deals insufficient damage to destroy the object then the spring mechanism triggers.
Encounter Design: One of the most iconic traps of D&D is the poison needle hidden in the lock of a treasure chest. Because traps with a spring mechanism are hard to detect, it’s best to either foreshadow them or include a brief window in which the effects can be countered by a well-prepared party (e.g. a poison with an onset time that doesn’t take effect instantly).

A tripwire is typically a thin piece of filament, such as fishing line or a giant spider’s spinneret, stretched across a passage holding a trap in tension. A creature moving into the tripwire while moving at a normal or fast pace triggers the trap.
Trap Examples: crossbow trap, falling net, spiderweb
Notice: A Wisdom (Perception) check allows a character moving cautiously to notice a tripwire. However, a character moving quickly (such as in the heat of combat) automatically triggers a tripwire they are unaware of.
Saving Throw: When a character triggers a tripwire when not moving quickly or in combat, they must make a DC 15 Dexterity saving throw. On a failed save, the tripwire is broken and the trap is triggered. On a successful save, the character’s foot presses into the tripwire but they’re able to stop themselves before breaking it entirely; the character can use an action to Disengage safely from the tripwire, and when disengaging in this way their speed is reduced to 5 feet until the end of their turn.
Disarm: Flying or levitating often avoids a tripwire altogether, as most tripwires are placed low to the ground. Taking an action to attack a tripwire can trigger the trap at a safe distance. An Intelligence (Investigation) check may be necessary to deduce where a tripwire leads to; once that area is located then thieves’ tools can be used to safely end the tension on the tripwire without triggering the trap.
Encounter Design: Because tripwires can be noticed by observant characters, they are best placed where the characters’ guards will be down or external pressure is a factor (in the form of monsters, other traps, or a time limit). As a “minimum investment” trap trigger, tripwires can be set up in dungeons where new occupants have moved in or otherwise have little time to prepare their defenses.
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That's great and all...but, er, "simplistic"? Common? Typical? Not sure what word to use. Now don't get me wrong. Damage is a good thing for traps to do, but for the more "Deadly" ones, I want them to be, well, "Deadly". I want a Poison Gas trap under "Deadly" to be something like "Con sv., DC 15; Failure = Death; Success = 1d8 hp per round for 10 rounds or until removed/neutralized". To me THAT is "Deadly"...it will kill you if you fail, and may kill you anyway if you succeed. I want a rolling rock trap to be "A 10-tonne sphere rolls down the hall; Dex sv., DC 15 to avoid for M, DC 10 for S, DC 20 for L; Failure = Death and most items on character destroyed".

To be fair, they are based on spell damage, and nothing says you can't make them functionally spells. And really, DC20/(22)4d10 is going to hit a lot and likely murder someone. they have a nice section on lethality. Just shift it up one level and it should be plenty lethal :)


Dances with Gnolls
I don't typically run traps, so using these on my players would be sickeningly evil of me... I like that idea.

I take their advertised perception checks to spot the trap and apply it to the idea that, the players roll if there is doubt in the matter. If I want them to see the trap, they will, and if there is no chance they can detect it until it is sprung, no amount of natural 20's on a skill check will save them.

Generally though, I like to live in that grey area with such things. Give the opportunity to spy something odd or have that, hair on the back of your neck feeling.

I am also a big fan of using an obvious trap, such as the pit trap to distract from greater dangers, or just to broadcast to the group that "Here, there be traps". Or not... really depends on the vibe I am going for, and who placed the traps, and for what purpose.

Initially I liked the more concise and delineated formatting.
But, upon deeper thought, I don't think it would work well in a published adventure. Unlike monsters, which are normally detailed elsewhere and then referenced in plain language, traps tend to be described in plain language in room descriptions. "When characters do X, then Y happens", and not separate trigger and effect paragraphs.

Similarly, complex traps are cool, but as presented take up too many space to ever be used in an adventure. Why use a complex trap that takes a full page when you could have two or three combat encounters?

Traps are already pretty sparsely used in published adventures.

I think these suffer from a problem similar to bad 4e skill challenges. The traps take 3+ actions to disarm because the challenge is designed to require multiple checks. Multiple checks as part of a multi-stage process are fine (i.e find the hidden compartment, unlock and remove the outer casing, disarm the mechanism). But when it's just repeating the exact same check three times, that's ridiculous. And not fun.
This doesn't particularly work at the table: if the action had no immediate reaction or benefit, why would you try again let alone twice more? From personal experience with a 4e trap, a player rolled a 20 and was excited, but the trap still needed two more checks for anything to happen. (I ruled the 20 count as two successes, but it still *felt* uneventful at the table as there was no effect that could be felt in play.)

This is especially problematic with spells and casting dispel magic. Even a 20th level wizard has to blow all their 3rd level spells to dispel a single complex trap. Who's going to do that?

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