I Cast...Brainstorm issue 3!

This week — Creating traps, three trapped doors, and a new cleric spell

Thanks for reading I Cast…Brainstorm!, a weekly newsletter with ideas to help make DM-ing easier, as well as game hooks, NPCs, magic items, monsters, encounters, towns, and other things to help make your D&D sessions more fun. Including traps! (And one of these weeks, we’ll get to puzzles, and puzzle-traps.)

I’m currently playing a lot of 5th edition D&D, but most things we talk about should be applicable to any edition, or even other RPG systems, with a tweak or two.

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Table of Contents

• Creating Fun and Fair Traps

  • Location, Function and Frequency of Use

  • Appearance and Mechanics

  • Difficulty Ratings

  • Threat Level

• Three Trapped Doors

  • Easy, for Character levels 1-4

  • Standard, for Character levels 5-10

  • The DM Is Angry at Character levels 05-10

• New Trickery Domain Cleric Spell

  • Delusions of Danger

• The Brainstormer Community

• Brainstorming Links

• What I’m DM-ing

• Gifts for Gamers

Creating Fun and Fair Traps

I think traps are one of the most fun elements in Dungeons & Dragons, and I would bet that every adventure I’ve played over 45 years has included a trap of some kind. Which makes sense — they were built into the game from the beginning. The adventure B1 In Search of the Unknown, by Mike Carr, is full of devious traps, and was released as part of the D&D Basic Set back in ‘76.

I love traps as both a player and a DM, and simple ones are pretty common in the game worlds I create. In a world without keypads and bike locks, poison darts are the next best thing, right? Whether simple or complex, common or rare, traps add tension and keep the characters on their toes, demonstrate that decisions have real consequences in the game world, and add a really fun element of surprise.

In my games, PCs might encounter more common types of traps — trapped locks on chests and doors, for example — multiple times, but traps should never become so common or similar that they lose the element of surprise, and feel like “Oh, this again”. Traps need to vary in style, complexity, location, lethality and other qualities to keep them fun and surprising, and most traps — especially the ones that would be easily recognized if encountered again — I only use once. This means I need a lot of traps for every campaign! When I need a new trap, I sometimes pull one from an adventure or book, or search online for something appropriate, (dmsguild.com has a lot of great ones), but I often just make them up.

Traps are a big topic, so I’m not going to delve too deeply into specifics (in this issue, anyway), but as quick overview, these are the things I think about when creating traps for my game.

Location, Function and Frequency of Use

Where is it, what’s the purpose of the trap, and how often is it bypassed?

The most common type of traps in my games are meant to be a deterrent to entry. A leader of a thieves guild has trapped the door to her bedroom to keep fellow thieves from snooping, for example. Or a wizard has trapped a chest in his magical laboratory that holds his most expensive and rare components, lest his apprentice be tempted to pocket a few.

All traps also have a frequency of use — are they meant to be bypassed every day, sometimes, rarely or never? The two examples above are what I consider “every day” traps — meaning, the trap is bypassed by the owner every day, or even more often than that. “Every day” traps should have simple, quick methods of bypass or suppression. No wizard wants to have to dial in a 15 letter secret code word every time he needs a spell component! Instead, the “key” to bypass an “every day” or “sometimes” trap should be something quick — saying a magic word, or pressing the correct rivet on the chest’s lid, or using a real key — so the owner can get past the trap and on with their day without too much fuss.

“Rarely" and “never” used traps are set in place for the long haul, possibly for centuries. A noble (and diabolical) family might trap the floor of the family’s mausoleum to deter grave robbers. The mausoleum is a place the family rarely visits, except when adding a new deceased family member, so the method of bypass or suppression could be more complex, and take longer to perform. In this case, perhaps with a holy (or unholy) ritual performed by a cleric of the family’s chosen god, as part of the process of interring the recently deceased.

Protecting treasure, deterring entry, catching prey, slowing pursuit, and the good old “evil lich creates deadly traps to murder as many adventurers as possible” are just some of the purposes you can use. Make up any purpose that fits into your game world and style of play, figure out a location and a bypass frequency for the trap, and you can devise a “key” that makes sense.

Appearance and Mechanics

What does the trap look like, and how does work?

This helps me create the description of the trap, both before and after its triggered, and helps me figure out the mechanics of finding, bypassing, disarming, and avoiding the trap. For example, a floor trap could work like so —

(We can add a purpose to this trap, too — maybe the tunnel is part of a prison, and the weight limit on the floor ensures that prisoners always move in single file, spaced far enough apart to keep it from falling open.)

Now I can decide what a character notices if they detect the trap — a slightly wider seam down the middle of the tiles, or maybe the glint off an iron hinge peeking out from under a chipped tile. I can also figure out (at least some of) the ways the characters can bypass the trap — they can avoid stepping on the floor, (by climbing along the walls, or flying), or use spikes to keep the sections of floor from swinging open, or if they’re particularly clever and figure out that the trap is triggered by weight, they can walk across one at a time.

Every trap should have a clear area of effect, and mechanics that you understand, even if those mechanics are “magic reasons”. This could look like a spring-loaded poison needle that affects just the character trying to pick a lock, a door rigged with alchemist fire that explodes when the handle is turned the wrong direction (in a 10’ x 10’ area in front of the door), or a ceiling in a 20’ x 20’ room that collapses if someone lifts a magic book off of a pedestal at its center. The specifics will make visualizing, describing and playing out the encounter so much easier.

Difficulty Ratings

How difficult should the trap be to discover and bypass?

The simplicity of the “key” for an every day trap doesn’t mean the trap is easy to see or disarm — what’s obvious to the owner could be almost impossible to find for everyone else. For me, the question of difficulty for bypassing or suppressing a trap has more to do with mechanical considerations, like the ability level of the characters, and how much of a chance of success they should have to both discover the trap, and to bypass, disarm or avoid it.

When I DM, anyone can make a (Wisdom) Perception check to examine something that they suspect could be trapped. I set a DC target for a success, and write the description of what they notice should they succeed. For example, a chest trapped with poison gas might be described in my notes as —

Once a trap is detected, the characters can try to disarm, bypass or avoid it. Disarming a trap can be done with a (Dexterity) Thieves' Tools check for mechanical traps, or maybe an (Intelligence) Arcana check for magical traps. I have no hard and fast rules about things like this. Any character can try to disarm a trap with some creativity, and I think we should always reward our players’ good ideas and ingenuity.

In any case, the disarm attempt will have a DC that I set mostly on difficulty and complexity. Every DMG includes helpful guidelines for creating traps, including the 2024 5th edition, which as a general rule uses fixed DCs for detecting and disarming. That’s a great starting point, but for me, DCs are more fluid, and I often adjust them when the encounter occurs, based on the current conditions of the characters, and the situation around the characters. I just need to figure out a ballpark success/fail number that fits the moment, and I’m good to go.

For example, if the characters are 3rd level, and the party rogue has a +8 with her thieves tools, and I think the trap should be easily disarmed, I would set the DC so the character will have something like a 75% chance of success. In other words, if I make the DC 13, the character succeeds on a 5 or better, (5 + 8 thieves tools = 13). Great! If the trap should be really difficult to disarm, (and — this is important — I’ve dropped clues about its difficulty, or just outright given the players that bit of information), then I can make the DC 23 or higher, so a success occurs only on a 15 or better. As an encounter develops, I figure out a success/fail chance that feels right, and then (usually) give the player the target DC just before they role, (which keeps the interaction honest and adds to the tension — win, win!).

Characters and encounter conditions are always changing. If the rest of the party creates a buffer around the character trying to disarm the trap, so they can concentrate better, I might drop the DC by 2, (or give Advantage on the roll). But if the character has lost their thieves tools, and is using improvised gear? I might raise the DC a bit, or give them Disadvantage on the roll. Or both! I can be such a rascal. The point is, use fixed DCs for everything if that’s your style, or adjust them on the fly, but either way, have a fair number ready to go, (with at least a small chance of success), so you can play out the encounter easily.

Threat Level

How deadly should the trap be if the characters fail to notice or to bypass it?

Trap lethality for me is mostly based on character level, which is also how the 2024 5th edition DMG breaks it down. But, again, where the DMG recommends fixed numbers, mine are very fluid.

I start as the DMG suggests, deciding if the trap should be a nuisance or deadly. Is this a minor situation — getting into a traveling merchant’s locked cart to look for evidence they’re connected to a faction of evil cultists? Or is the trap part of a big story moment — trying to get into the king’s vault to steal the Magical Macguffin after eighty game sessions? Bigger moments = higher rewards = higher risk.

Then consider the characters’ levels and hp, and add in the complexity of the trap, the competence of the creature that set the trap, the current resources available to the characters to respond to the traps’ consequences, the chances the party will be able to rest soon, and…well, anything else you think is important. I mix that all together and come up with a ballpark number that feels fair. For 1st level characters, a nuisance trap might do 1d10 damage as the DMG suggests, or maybe 1d4, if the characters have are scraping by on their last resources.

And yes, I hear you, DMs that prefer to set numbers and have their players just deal with them! That’s a fun and perfect way to go, too. My style of DM-ing is often about managing the story and the dramatic tension throughout a session and campaign, so I adjust a lot as I go. Of course, there are as many ways to approach traps in TTRPGs are there are DMs.

You also might design your traps around factors that have nothing to do with the characters’ levels, or even the story. Consider the kind of game, and play-style, you and your players enjoy most. Does everyone like a grimdark world where a wrong move could result in a character’s death? Or a more forgiving world, where the characters are more likely to survive, and affect the story and the game world over a long period of time? In that case, you can create traps with less lethal, but still impactful, consequences — a poisoned condition that can only be cured with a plant they have to go on a quest to find, for example — so you and your players can enjoy the fun tension and surprise of traps, however you like to play.

Three Trapped Doors

Drop these trapped doors into your campaign, and let us know how much your players (dis)like them!

Easy, for Character levels 1-4

This trapped wooden door has a brass handle with a decorative thumb latch, and no visible lock. Unless a button is held down on the back of the handle when the thumb latch is pressed, a poisoned needle will spring up from the latch and pierce the opener’s thumb.

A successful DC 12 (Wisdom) Perception check will detect the trap, (a worn part on the back side of the iron handle where countless fingers have pressed the hidden button, or the tiny needle hole hidden in the design on the thumb latch).

A DC 14 (Dexterity) Thieves Tools check will disarm the trap. A failed attempt to disarm it triggers it, and if the attempt fails by 5 or more, the needle pierces the hand of the character attempting the disarm (if they’re close enough to for the needle to make contact and haven’t taken other precautions).

If the needle pierces the skin of a character, the PC takes 1 piercing damage, and must make a successful DC 12 Constitution save or take 1d10 poison damage.

Standard, for Character levels 5-10

This rusty iron door is locked, and has an round iron knob in the center, about 3’ off the floor. Above the knob is a keyhole. The lock can be picked with a successful DC 18 (Dexterity) Thieves Tools check, but unless the actual key is used, the first creature that steps through the door will trigger a hidden guillotine that drops straight down from the top of the jamb, disappearing into a thin slit in the floor.

A successful DC 18 (Wisdom) Perception check will detect the trap, (if they shine a light under the door they can see the thin slit where the blade disappears, or they can glimpse a second mechanism inside the lock that allows the proper key to disarm the trap).

A DC 20 (Dexterity) Thieves Tools check will disarm the trap.

A creature who triggers the guillotine must make a DC 18 Dexterity Save or take 3d10 slashing damage. A successful save results in half damage.

The DM Is Angry at Character levels 05-10

This wooden exterior door is painted black, as are its iron hinges, and is opened with a simple iron bolt that slides toward the center of the door. The bolt is trapped with a 7th level Glyph of Warding. Unless the word “Grounded” is spoken while holding the bolt, when the bolt is slid open a Spell Glyph triggers and casts Reverse Gravity, targeting the creature who slid the bolt.

A successful DC 20 (Intelligence) Investigation check will detect the trap, (faint, tiny runes in the lower left corner of the door, almost invisible due to the black paint), and a DC 20 (Intelligence) Arcana check on the runes will reveal the 7th level Spell Glyph, but not the exact spell. Casting Dispel Magic on the door, and making a successful DC 17 ability check, using your spellcasting ability, will dispel the Glyph.

If the Glyph isn’t dispelled, a creature who slides the bolt open triggers the spell, and becomes the target (and center) of a 50’ radius, 100’ high Cylinder. The opener and all other creatures and objects in the spell’s area of effect, that aren’t anchored to the ground, fall upward to the top of the Cylinder. The opener can make a DC 20 Strength saving throw to hold onto of the bolt, and avoid the fall upward.

When an affected creature or object reaches the Cylinder’s top, it hovers there for the duration of the spell. After 1 minute, the spell ends and affected creatures (and objects) fall downward, taking 10d6 bludgeoning damage upon contact with the ground, unless their fall is slowed, or their landing is cushioned.

New Trickery Domain Cleric Spell

I once played a really fun Dragonborn Tempest Cleric (2014 5e rules) in a mostly wilderness adventure at sea, and I loved using Call Lightning — a long-lasting spell that could be aimed at different enemies throughout a battle, as long as I could keep concentration. I’ve been playing around with homebrew spells with similar mechanics, but for other domains and disciplines, like this version, which is themed around Clerics of the Trickery Domain, and other characters who specialize in Illusion magic.

Delusions of Danger

Level 3rd
Casting Time 1 Action
Range/Area 120 ft. (60’ radius area of effect)
Components V, S
Duration Concentration, 2 Minutes
School Illusion
Attack/Save INT Save
Damage/Effect Psychic/ Control

You create a 60’ radius area of roiling mist (of any color you choose) on the ground, originating at a point you can see within 120’. The mist creates a heavily obscured area filling the circle to a height of 2’ from whatever surface its cast on.

When you cast the spell, choose a point you can see in the spell’s area that’s adjacent to at least one enemy. A phantasm that looks exactly like you appears from the mist at that point, wielding a weapon of your choice. The phantasm immediately attacks all adjacent enemies. The attacked creatures make an Intelligence saving throw, taking 2d10 Psychic damage on a failed save, believing the damage type to be whatever is most appropriate for the phantasm’s illusory weapon. On a successful save, the target takes no damage, believing the attack missed. After all attacks, the phantasm drops back into the mist.

Each round you maintain Concentration, as a Magic action, you can cause another phantasm to appear at any spot you can see in the spell’s area and adjacent to at least one enemy, with the same effects.

All phantasms feature sound, texture, color, temperature, and other effects to make them seem as real as possible to the targets.

Using a Higher-Level Spell Slot — For every spell slot above 3rd, you can make one additional phantasm simultaneously appear from a different point inside the spell’s area and adjacent to at least one enemy, with the same effects. Phantasms must all attack different targets.

Spell Tags: Damage, Control, Deception
For: Clerics of the Trickery Domain, Illusionist Wizards, Bards

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Brainstorming Links

If you love D&D and other RPGs as much as I do, you probably already know about the folks below, who are real inspirations to me. If you haven’t already, please check ‘em out!

DMDave — on point analysis of D&D rules, and a ton of fun ideas
https://bsky.app/profile/dmdave.bsky.social

Treantmonk — years of helpful advice and clever ideas
https://www.youtube.com/@TreantmonksTemple

RPGBot — whip smart critique and explanations of 5e rules
https://rpgbot.net/

The Arcane Library — masterpiece adventures, and Shadowdark, too!
https://www.thearcanelibrary.com

Sly Flourish — a DM’s best friend who is also a better DM
https://www.slyflourish.com/

What I’m DM-ing

• A weekly Curse of Strahd campaign via Roll20 using 2014 5th edition rules — 54 sessions so far

• A weekly Rime of the Frostmaiden campaign, in-person with 2024 5th edition rules — 2 sessions

• A series of one-shots at a bi-weekly game at a bar — 18 sessions

• and a couple campaigns with my kids, when schedules align! (Scheduling is hard.)

What I’m Playing

• A 5th ed. Dragonlance campaign as a 9th level Tinker Gnome Gadgeteer Rogue, named Professor Flondersnoot (paused after Dragons of Dreams)

• About to start playing Vecna: Eve of Ruin as a 9th level Halfling great-weapon Fighter — Flimm the Clumsy

• And in all my free time, I play a LOT of Hearthstone!

Gifts for Gamers

You can find great gifts for the gamers in your life at Total Party Kits, which features all-original designs, by yours truly, on shirts, hats, mugs and other fun things!

 www.totalpartykits.etsy.com

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