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Traps Revisited

The rules for traps in the Dungeon Master's Guide provide the basic information you need to manage traps at the game table. The material here takes a more elaborate approach—describing traps in terms of their game mechanics and offering guidance on creating traps of your own using these new rules.

Trap Categories

1. Simple Traps

  • Definition: A simple trap activates and is thereafter harmless or easily avoided. Examples include:
    • A hidden pit at the entrance of a goblin lair.
    • A poison needle that pops from a lock.
    • A crossbow rigged to fire when an intruder steps on a pressure plate.

2. Complex Traps

  • Definition: Complex traps involve multiple components or stages, often remaining a threat for longer and requiring more effort to avoid or disable. These might be detailed in a future section.

Elements of a Simple Trap

1. Level and Threat

  • Level Range: Equivalent to one of the tiers of play (levels 1-4, 5-10, 11-16, and 17-20).
  • Threat Level:
    • Moderate
    • Dangerous
    • Deadly

2. Trigger

  • Description: The condition that activates the trap.
  • Examples:
    • A pressure plate that, when stepped on, triggers a dart.
    • A hidden tripwire that releases a boulder.

3. Effect

  • Description: What happens after the trap is triggered.
  • Details:
    • Targets: What the trap affects (e.g., all creatures within a certain area).
    • Attack Bonus or Saving Throw DC: The trap's attack roll or the DC for a saving throw to avoid the effect.
    • Consequences: The effects of a hit or a failed saving throw (e.g., damage, conditions like poisoned or stunned).

4. Countermeasures

  • Detection and Disabling: Ways to detect or defeat the trap, usually involving ability checks or magic.
  • Consequences of Failure: What happens if the attempt to disable the trap fails.

Running a Simple Trap

1. Preparation

  • Passive Perception: Note the characters' passive Wisdom (Perception) scores beforehand to see if they detect the trap.

2. Triggering the Trap

  • Activation: Apply the trap's effects as specified when it is triggered.

3. Handling Countermeasures

  • Player Creativity: Be open to players' ideas for defeating the trap. The trap's description is a guideline, not a strict limit.
  • Player Specificity: Encourage players to be specific about how they wish to disable the trap (e.g., positioning, tools used).

Example Simple Trap

Poison Dart Trap (Levels 1-4, Dangerous)

  • Trigger: A pressure plate hidden beneath a loose stone.
  • Effect:
    • Targets: The creature that steps on the pressure plate.
    • Attack Roll: +5 to hit.
    • Damage: 2d10 poison damage on a hit.
    • Secondary Effect: The target must succeed on a DC 13 Constitution saving throw or be poisoned for 1 hour.
  • Countermeasures:
    • Detection: DC 15 Wisdom (Perception) check to notice the pressure plate.
    • Disabling: DC 15 Dexterity check with thieves’ tools to disable the plate without triggering the trap.
    • Failure Consequence: If the disabling attempt fails, the trap activates.

Making Traps Meaningful

To ensure that the characters will encounter the traps you've set, it might be tempting to use a large number of traps. However, it's better to resist this urge. If your encounters or adventures are riddled with too many traps, the characters might become overly cautious. This can slow down the game's pace as players meticulously search every inch of the dungeon for trip wires and pressure plates.

Traps are most effective when their presence comes as a surprise, not when they are so frequent that the characters spend all their effort watching out for the next one.

Example Simple Traps

Below are some example simple traps that can be used in your adventures or serve as models for your own creations.

Bear Trap

  • Type: Simple Trap (Level 1-4, Dangerous Threat)
  • Description: A bear trap resembles a set of iron jaws that spring shut when stepped on, immobilizing the victim.
  • Trigger: A creature that steps on the bear trap triggers it.
  • Effect:
    • The trap makes an attack against the triggering creature with a +8 attack bonus.
    • On a hit, the trap deals 5 (1d10) piercing damage.
    • The creature’s speed is reduced to 0 until it breaks free of the trap with a DC 15 Strength check.
  • Countermeasures:
    • A successful DC 10 Wisdom (Perception) check reveals the trap.
    • A successful DC 10 Dexterity check using thieves' tools disables the trap.

Crossbow Trap

  • Type: Simple Trap (Level 1-4, Dangerous Threat)
  • Description: A favorite trap of kobolds and other trap-reliant creatures, it consists of a trip wire connected to hidden heavy crossbows aimed down a hallway.
  • Trigger: A creature that walks through the trip wire triggers the trap.
  • Effect:
    • The trap makes two attacks against the triggering creature.
    • Each attack has a +8 attack bonus and deals 5 (1d10) piercing damage on a hit.
  • Countermeasures:
    • A successful DC 15 Wisdom (Perception) check reveals the trip wire.
    • A successful DC 15 Dexterity check using thieves' tools disables the trip wire, but a check with a total of 5 or lower triggers the trap.

Falling Portcullis

  • Type: Simple Trap (Level 1-4, Moderate Threat)
  • Description: Designed to block exits or passageways, this trap causes a portcullis to drop when activated.
  • Trigger: A creature that steps on the pressure plate triggers the trap.
  • Effect:
    • An iron portcullis drops from the ceiling, blocking an exit or a passageway.
  • Countermeasures:
    • A successful DC 20 Wisdom (Perception) check reveals the pressure plate.
    • A successful DC 20 Dexterity check using thieves' tools disables the pressure plate.

Fiery Blast

  • Type: Simple Trap (Level 5-10, Dangerous Threat)
  • Description: In a temple of Pyremius, a floor mosaic triggers a fiery blast to protect the fire opals displayed by the priests.
  • Trigger: Stepping on the mosaic triggers the trap, unless the creature is wearing a holy symbol of Pyremius.
  • Effect:
    • A 15-foot cube of fire erupts, covering the pressure plate and the surrounding area.
    • Each creature in the area must make a DC 15 Dexterity saving throw, taking 24 (7d6) fire damage on a failed save, or half as much on a successful one.
  • Countermeasures:
    • A successful DC 15 Wisdom (Perception) check reveals ash and burn marks.
    • A successful DC 15 Intelligence (Religion) check can destroy the trap by defacing a key rune on the mosaic.

Net Trap

  • Type: Simple Trap (Level 1-4, Dangerous Threat)
  • Description: Goblins use this trap to capture intruders with a falling net.
  • Trigger: A trip wire rigged to a large net is triggered when broken.
  • Effect:
    • A net falls, covering a 10-foot-by-10-foot area centered on the trip wire.
    • Any creature in this area must succeed on a DC 15 Dexterity saving throw or be restrained.
  • Countermeasures:
    • A successful DC 15 Wisdom (Perception) check reveals the trip wire and net.
    • A successful DC 15 Dexterity check using thieves' tools disables the trip wire without triggering the trap.

Pit Trap

  • Type: Simple Trap (Level 1-4, Moderate Threat)
  • Description: A 10-foot-deep pit concealed by a canvas cover, often used to block entrances to monster lairs.
  • Trigger: Anyone stepping on the canvas might fall into the pit.
  • Effect:
    • The triggering creature must make a DC 10 Dexterity saving throw.
    • On a successful save, the creature catches itself on the pit's edge.
    • On a failed save, the creature falls into the pit and takes 3 (1d6) bludgeoning damage.
  • Countermeasures:
    • A successful DC 10 Wisdom (Perception) check reveals the canvas and the 1-foot-wide ledge around the pit.

Poison Needle

  • Type: Simple Trap (Level 1-4, Deadly Threat)
  • Description: A tiny needle hidden in a lock to deter thieves from plundering treasure.
  • Trigger: Attempting to pick or open the lock triggers the trap.
  • Effect:
    • The triggering creature must make a DC 20 Constitution saving throw.
    • On a failed save, the creature takes 14 (4d6) poison damage and is paralyzed for 10 minutes.
    • On a successful save, the creature takes half damage and is not paralyzed.
  • Countermeasures:
    • A successful DC 20 Wisdom (Perception) check reveals the needle.
    • A successful DC 20 Dexterity check using thieves' tools disables the needle.

Scything Blade

  • Type: Simple Trap (Level 5-10, Dangerous Threat)
  • Description: Moving blades that sweep through a chamber, often activated by a lever or similar device.
  • Trigger: Pulling the lever activates the trap.
  • Effect:
    • Each Medium or larger creature in a 5-foot-wide, 20-foot-long area must make a DC 15 Dexterity saving throw.
    • On a failed save, the creature takes 14 (4d6) slashing damage.
    • On a successful save, the creature takes half damage.
  • Countermeasures:
    • A successful DC 15 Wisdom (Perception) check reveals scrape marks and bloodstains.
    • A successful DC 15 Dexterity check using thieves' tools disables the lever.

Sleep of Ages

  • Type: Simple Trap (Level 11-16, Deadly Threat)
  • Description: A pressure plate that unleashes a spell, sending intruders into a deep slumber.
  • Trigger: Stepping on the pressure plate triggers the trap.
  • Effect:
    • The trap casts a sleep spell centered on the pressure plate, using a 9th-level spell slot.
  • Countermeasures:
    • A successful DC 20 Wisdom (Perception) check reveals the pressure plate.
    • A successful DC 20 Intelligence (Arcana) check disables the trap.

Designing Simple Traps

You can create your own simple traps using the following guidelines. Modify the DCs and damage values as necessary to adapt the traps for different levels and threats.

Purpose

Before creating the details of your trap, think about its purpose. Why would someone build such a trap? Consider the trap's creator, their purpose, and the location the trap protects.

Here are a few general purposes a trap might have:

  • Alarm: Alerts the area's occupants of intruders.
  • Delay: Slows down enemies, giving inhabitants time to mount a defense or flee.
  • Restrain: Keeps victims in place, making them easy targets for guards.
  • Slay: Designed to eliminate intruders with lethal measures.

Level and Lethality

Determine the trap's level range and its lethality:

  • Level Ranges: 1-4, 5-10, 11-16, 17-20.
  • Lethality:
    • Moderate: Unlikely to kill a character.
    • Dangerous: Deals significant damage.
    • Deadly: Could reduce a character to 0 hit points.

Trap Save DCs and Attack Bonuses

Use the following table to determine the trap's saving throw DC, check DC, and attack bonus:

Trap Danger Save/Check DC Attack Bonus
Moderate 10 +5
Dangerous 15 +8
Deadly 20 +12

Damage Severity by Level

Use the following table to determine the typical damage a trap deals:

Character Level Moderate Dangerous Deadly
1-4 5 (1​d10) 11 (2d10) 22 (4d10)
5-10 11 (2d10) 22 (4d10) 55 (10d10)
11-16 22 (4d10) 55 (10d10) 99 (18d10)
17-20 55 (10d10) 99 (18d10) 132 (24d10)

Spell Equivalent by Level

Use the following table to determine the appropriate spell slot level for the trap:

Character Level Moderate Dangerous Deadly
1-4 Cantrip 1st 2nd
5-10 1st 3rd 6th
11-16 3rd 6th 9th
17-20 6th 9th 9th + 5th

Triggers

Decide what causes the trap to activate and how characters can discover the trigger. Examples include:

  • Pressure plate
  • Trip wire
  • Doorknob turned the wrong way
  • Opening a door or chest

Effects

Design the trap’s effects using the tables provided. For more complex traps, consider using a spell as a starting point.

Disarming a Simple Trap

Determine how the trap can be disarmed or avoided. Consider the following:

  • Dexterity check using thieves’ tools: Used to disable mechanical traps.
  • Strength check: Often used to thwart traps that can be destroyed.
  • Intelligence (Arcana) check: Used to disable magical traps.

Placing a Simple Trap

Context and environment are critical. Consider where the trap will be most effective and how it fits within the dungeon’s layout.

Complex Traps

A complex trap poses multiple dangers and remains active over several rounds until avoided or disabled. These traps require more effort to overcome and involve multiple checks.

Describing a Complex Trap

  • Level and Threat: Use the same level and severity designations as for simple traps.
  • Trigger: Complex traps often have multiple triggers.
  • Initiative: Complex traps act on a specific initiative count (10, 20, or both).
    • Active Elements: The trap’s effects on its turn.
    • Dynamic Elements: Threats that evolve over time.
    • Constant Elements: Ongoing threats outside the trap’s turn.
    • Countermeasures: Steps to disable the trap, usually requiring multiple checks.

Running a Complex Trap

A complex trap functions like a legendary monster. It acts on its initiative counts, applies effects, and evolves over time. Award experience points based on the trap’s level and threat when the characters overcome it.

Designing Complex Traps

Consider the trap’s purpose, map the area it affects, and design its active, constant, and dynamic elements. Triggers should be foolproof, and defeating the trap usually requires multiple successes.

This guide should help you design and implement traps that are both meaningful and challenging for your players.