Return to Undermountain
Return to Undermountain Traps
By Matthew Sernett

When thinking about putting traps in your dungeons, you might imagine something from one of the Indiana Jones movies. The dramatic tension of the trap being sprung and the tense action of the heroes trying to escape it make for great cinema. Unfortunately, traps in D&D work more like designers intend them to work -- as impediments.

An individual puts a trap in place to injure, slow, kill, or capture someone else, and traps in D&D work precisely like that -- except they're often having those effects on your game in addition to the PCs. Traps make many players slow their dungeon delve to a crawl as they tentatively check every door, chest, and square of floor they encounter. The event is so common that the 10-foot pole (for poking at potential traps) and taking 10 minutes to open a door have become clichés.

Even if your group of players isn't the type to let a couple of traps slow them down, traps can ruin your game.

Traps usually come in two varieties: game pausing and game stopping. A game-pausing trap deals some damage or causes some other deleterious effect that the PCs can remedy with a few rounds of actions and spellcasting. The trap goes off, affects a PC or two, and then the PCs use some of their resources to recover. The net effect of the trap was simply to put the real action of the adventure on pause for a while. A game-stopping trap kills a PC or has an effect that makes the players stop and rest. These traps essentially stop the game as your players retreat to a place of safety or leave the dungeon altogether. Both types of traps make the game less fun. Instead of putting tense action in your game, they give you aggravated and bored reaction.

Add to all this the fact that PCs often possess the means to detect, disarm, and avoid traps.

For these reasons many DMs avoid putting traps in their adventures, but what's a dungeon without devious devices to bedevil the PCs?

Good Traps

Good traps increase the dramatic tension in your game and create action. They make sense in the dungeon, and they help move the adventure farther on its course. When thinking about including a trap in your adventure, think about the classic questions: who, what, where, when, how, and why, and then think about the action that should take place because of the trap.

Who: Who put the trap there? The trap will work differently, have a special purpose, and look different depending on who put it in place. A dwarf's pit trap should be distinct from one built by drow. Considering who built the trap and having that be meaningful will add flavor to the encounter with the trap and inform the players and their PCs about the environment of the adventure.

What: What kind of trap is it? Is it intended to injure, slow, kill, or capture? What effect is it likely to have on the PCs? Answering these questions will help you determine if the trap you're thinking of using is game pausing, game stopping, or good.

Where: Where is the trap? Think about how the placement of the trap affects your players' mindsets. Placing a trap on a treasure chest might make the players suspicious of other chests they find in the dungeon, but that's much better than a trap placed on a random square in a hall, because the square in the hall makes the players suspicious of every place they walk.

When: When was the trap placed there? Maybe the trap is so old that it jams when the PCs set it off, giving the tension of the trap without the negative repercussions and perhaps giving them some overconfidence. Maybe a wandering monster already set it off. When is it reset? Maybe the PCs have a chance to encounter the trap keeper on his rounds of checking and oiling traps. When does the trap come into play based on the pace of the adventure? If you put a deadly trap on the door to the dragon's lair, the players might just turn around and leave rather than face the dragon after getting hit with the trap.

How: How do the PCs avoid the trap? How does the person who put the trap there avoid it? How does the trap work in the confines of the dungeon? If it's a mechanical trap, how does someone get at its mechanism when it needs fixing or resetting? How was it built? Answering these questions can inform the construction of the dungeon and your placement of the trap, and it can give you something interesting to tell the players when the rogue makes her Search or Disable Device check.

Why: Why are you putting the trap in the adventure? Why did some dungeon inhabitant put it there? Why does it work like you want it to work? Knowing the answer to these questions makes your inclusion of the trap make sense to the players' understanding of the world and assures you that the trap does what you want it to.

Action: What happens if the trap is set off? What can the PCs do if that happens? If they just make a couple of rolls and take some damage, it's probably not a good trap by itself in the dungeon. Yet if that trap is in a room where the PCs have to fight some enemies, that boring, game-pausing trap can be a tactical element to the battlefield that the PCs and their foes try to use to their advantage. Traps work best when they create drama or heighten drama. A trap on a door or in a hallway is unlikely to do that.

Using Traps from the Dungeon Master's Guide

The Dungeon Master's Guide presents many interesting traps, but without some creativity, all of them have the potential to be mere game-pausing traps and many could be game stoppers.

Attack Traps: Traps that just make attack rolls and deal damage work best as an addition to an encounter with something else. Think of them as spice added to the main course. Perhaps the PCs encounter a monster in a room with scything blades that swing from the ceiling when the PCs or the monster steps on the wrong square. Maybe the PCs have to run through a hall that fires poisoned darts so that they can escape a cave-in.

Blocking Traps: Blocking traps prevent the PCs' access to a location. A cave-in, a falling portcullis, or a sliding wall are all examples of blocking traps you might employ against the PCs. Blocking traps can make an encounter more difficult by dividing the PCs or giving a villain a means of escape. They can also direct the PCs movement through a dungeon. Be careful not to be heavy-handed with blocking traps. You shouldn't use them to railroad the PCs on a particular path.

Capture Traps: Capture traps hold one or all the PCs trapped. A capture trap might take the form of a room that seals closed once the PCs enter, a burst of paralyzing gas, or any other trap that incapacitates but does not kill. Usually, some foes of the PCs come by to take them captive once the trap is set off. Be judicious about when to use such traps. No one taking the PCs captive would leave them with their equipment, and players often hate having their PCs' equipment taken more than having their characters die. Use capture traps rarely.

Pit Traps: Try not to use pit traps in a combat encounter unless the pits are relatively easy to get out of or they add to the encounter by giving those who fall in the pits something else to fight. If the PCs encounter a pit trap while walking through the dungeon, use the trap as a means of propelling the adventure forward instead of pausing it. Perhaps a secret door is at the bottom of the pit, or maybe a past victim of the pit lies at the bottom with a partial map of the dungeon. Think of pit traps as an appetizer for the main course of your adventure.

Saving Throw Traps: Traps that require a saving throw and then deal damage are like attack traps. Use them as spice in an encounter.

Using Traps from the Dungeon Master's Guide II

The Dungeon Master's Guide II presents several new traps. Many fall into the categories noted above, but a few offer some interesting alternatives.

Booby Trap: The booby traps make great spice in an encounter. In particular, the knockback trap becomes a lot more interesting if there's a pit or fire into which a PC can be knocked.

Fire or Water Summoning Trap: These traps are encounters all by themselves. Using these traps as a pattern, you could have a cave-in trap that summons an earth elemental.

Haunting Trap: The haunting trap presents a great way to bring into the rules the spooky atmosphere of a place frequented by undead. Several haunting traps throughout a haunted location could make it seem very unnatural and unnerving.

Spell Turret: Like the fire summoning trap, the spell turret trap can be its own encounter complete with monsters. Such a trap might even cast several summoning spells and bring in guardian creatures to delay the PCs while the real guards come running due to the sound of combat.

Classic Traps of Undermountain

Ruins of Undermountain presented several new traps on handy reference cards. Many of the traps from that product now appear in the Dungeon Master's Guide but under different names. Here are updates to the current rules for the rest of the traps. You'll find trap statistics first (if any), followed by descriptions and other information.

Falling Door Trap: CR 2; mechanical; touch trigger; manual reset; Atk +10 melee (4d6 bludgeoning); multiple targets; DC 15 Reflex save avoids being caught under the door, assuming the affected creature can move to an adjacent unaffected square; creatures caught under the door can be freed by a DC 20 Strength check or they can free themselves with a DC 20 Escape Artist check; Search DC 20; Disable Device DC 20.

The falling door trap takes effect when someone pulls on the handle to open the door. The 10-foot tall door falls toward the opener and affects any creatures in the squares in front of the door and the square beyond that square.

False Bait Pit Trap: The false bait pit trap combines an obvious pit trap with scything blade traps in the wall. The PCs encounter the obvious signs of a pit trap, such as a slab of stone different from others in the dungeon, but they can see what looks like a narrow ledge of safe stone around the cover of the pit. If the PCs edge around the pit, the hidden scything blade traps come out of the walls to strike the PCs while they are balancing on the narrow safe area. PCs who fail their Balance checks due to damage suffered fall onto the pit trap and suffer its effects.

To replicate this trap, simply combine two traps from the Dungeon Master's Guide: the CR 2 pit trap (now CR 1 because it is so obvious) with the CR 1 scything blade trap. This makes the traps an EL 2 encounter.

Green Slime Door Trap: CR 4; mechanical; touch trigger; manual reset; never miss (character covered in green slime; 1d6 Con); onset delay (1 round [to scrape off]-- see page 76 of the Dungeon Master's Guide for more information); Search DC 20; Disable Device DC 20.

Tampering with the door causes hatches on it to open and spill out green slime in the square in front of the door.

Inhabited Pit Trap: This pit is inhabited by a swarm! Simply combine any pit trap from the Dungeon Master's Guide and any swarm to create a scary pit-trap encounter. It works best if the pit is 10 feet wide. Use the CR of the pit and swarm you choose to determine the EL.

Kissing Maiden Trap: CR 2; mechanical; location trigger; manual reset; Atk +12 (3d6 bludgeoning); unavoidable bull rush attempt by Medium creature with 18 Strength; Search DC 22; Disable Device DC 19.

When a PC steps on a hidden pressure plate, a portion of the floor slides away and a post pivots up from the floor to slam into the character (think of stepping on a rake). They're called kissing maidens because many of the posts are covered in an iron sculpture of a woman. Smaller versions set at about waist height for a human often have metal heads cast to look like rams' heads.

Leghold Trap: The leghold trap is similar to the animal traps used by hunters but sized for a human. Use the rules for the hobbling trap presented in Dungeon Master's Guide II.

Mobile Pit: A mobile pit works like any other pit trap, but it's more like a portable hole, and a victim of the trap falls into in an extradimensional space. The pit then moves through the dungeon, whisking a trapped creature to a predetermined location. Although unintelligent, mobile pits might even travel a regular route like a patrolling creature. Mobile pits can move at different speeds, but most travel at a regular speed of 30 feet per round.

Simply apply the mobile quality to any pit trap. You should increase the CR of a mobile pit by at least 1 and maybe by 2 or more depending on how fast it moves and toward what dangers it carries a victim.

Pit with Bladed Chute Trap: CR 3; mechanical; location trigger; manual reset; DC 20 Reflex save avoids; 30 ft. deep (3d6 slashing, 3d6 fall); Search DC 20; Disable Device DC 20.

This narrow pit has blades in the wall that cut a victim as he falls and that make climbing out of the pit perilous.

Punishment Pit Trap: Those who fall in a punishment pit are attacked by mechanical arms in the bottom of the pit. To make a punishment pit, simply put the CR 5 moving executioner statue trap from the Dungeon Master's Guide at the bottom of whatever pit trap you use. Combine the CRs according to Table 3-1 in the Dungeon Master's Guide to figure out the final EL.

Reverse Gravity Pit Trap: Those who fall in a reverse gravity pit strike the bottom only to be flung to the ceiling and dropped to the bottom again. Combine whatever pit trap you like with the reverse gravity Trap from the Dungeon Master's Guide. Figure out the final average damage from the multiple falls and increase the CR of the lowest-CR trap by 1 per every 7 points higher the average damage is than the combined average damages of both traps. Once you do that, combine the CRs according to Table 3-1 in the Dungeon Master's Guide to figure out the final EL.

Snare Trap: CR 1; mechanical; location trigger; manual reset; DC 25 Reflex save avoids; creature pulled up to ceiling suddenly and held there until it makes a DC 15 Escape Artist check or until the cord holding the PC suffers 3 points of slashing damage (the metal cord has hardness 8).

A snare trap works like an animal snare. A PC caught in the trap is hauled upward by his foot to the ceiling.

Stone Restraints Trap: CR 2; magic device; location trigger; no reset; spell effect (stony grasp, 7th-level wizard, +11 grapple check against victim, attempts to grapple and pin for 14 rounds, grappling arm has AC 18, hardness 8, and 28 hit points); Search DC 28; Disable Device DC 28.

The stone restraints trap (or stony grasp trap) causes the walls or floor to grow an arm and grab its victim. It's effectively a stony grasp trap. See Complete Arcane for a description of the stony grasp spell. To affect multiple creatures, place multiple traps in the area.

Puzzle Traps

This article deals with typical dungeon traps; puzzle traps are a horse of a different color. Puzzle traps are usually obvious and often guard some location or object in an adventure. They're called "puzzle" traps because the PCs often have to figure out the puzzle of how to dismantle, disarm, or circumvent them.

Puzzle traps can make great encounters on their own, but unless you put a fair amount of thought behind one, it easily can turn into a game-pausing or game-stopping trap. With a puzzle trap, you need to make sure that every PC can contribute to the solution.

It's often best if the "puzzle" isn't a riddle or a logic game that the players must figure out. A riddle or logic puzzle might work if everyone in your group likes such things, but it's likely that either one person will swiftly figure it out or the whole group will be stymied.

Instead, consider a puzzle that relies on the characters' abilities. For example: Perhaps the cleric and fighter have to push something heavy while the wizard levitates the rogue to an otherwise inaccessible lock.

Need more information? Check the Return to Undermountain: An Introduction for more details.

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About the Author

Once editor-in-chief of Dragon Magazine and now a game designer at Wizards of the Coast, Matthew Sernett wrote in a Dragon editorial that there's nothing in D&D he likes better than when the adventurers flee through the dungeon, running pell-mell through traps and past monsters because what chases them is worse. When he wrote that, Matthew was thinking about Undermountain.


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