Complex traps vs. “roll + effect”
When we want to use traps or environmental hazards in D&D, sometimes, designing complex mechanics can be fun. But sometimes we need a quick trap to add some obstacles to an improvised dungeon, or we want to use a trap as a complication the bad guy throws at the characters chasing them. In these cases, we can default to roll and combine it with a flavorful effect.
The roll: attack or save?
When players stumble into a trap, we roll an attack, or the players make a saving throw. After a while this becomes intuitive but the choice is also largely arbitrary. I have previously argued for letting players roll the dice as often as possible. In a nutshell, however, if something weapon-like targets a character it’s an attack roll. If the characters resist some area-of-effect trap, it’s a saving throw.
Is a large bone shard launched at a character? Roll an attack. Are the characters slowly suffocated by an invisible gas? Have them make a saving throw.
Set a DC
We set the DC or bonus to hit based on the situation. Mike Shea from slyflourish.com gives us a neat trick to quickly set these numbers. Rate the difficulty of the trap or hazard on a scale from one to ten. That is your bonus to hit. For a saving throw, add 10 to the number to determine the DC.
Effects from many sources
Then we combine this roll with a flavorful effect. There are many sources we can pull such effects from on the fly. We can have the trap deal a situationally appropriate amount of damage, and add a suitable condition. We can use an environmental hazard from Tasha’s Cauldron of Everything. Sometimes a madness effect from the Dungeon Master’s Guide can represent a psychological threat. Alternatively, we can use a spell as a template for a trap. For example, the invisible gas could function like the cloudkill spell.
Examples of traps, rolls, and effects
The following table gives an overview of six different types of D&D traps, the type of roll associated with them, and spell effects or other effects to use with the trap.
| Type | Roll | Spell effect | Other effects |
|---|---|---|---|
| Gas | CON save | cloudkill, stinking cloud | Madness effect (DMG) |
| Explosion | DEX/STR save | fireball, burning hands, cone of cold, lightning bolt, thunderwave | saving throw to avoid damage, and being pushed 10-20 feet |
| Weapon | attack vs. AC | conjure barrage, conjure volley, shadow blade | attack roll for bludgeoning/piercing/slashing damage |
| Pit/debris | DEX save or attack vs. AC | catapult, conjure barrage, conjure volley | saving throw to avoid falling damage/bludgeoning damage |
| Energy | CON save | magic missile, blight, guardian of faith | “Eldritch Storm” (TCoE) |
| Mental | WIS/INT save | phantasmal killer, confusion | Madness effect (DMG); “Far Realm Effect” (TCoE) |
D&D Traps made easy
When we improvise D&D traps or a hazards in this way, we grab whatever pre-existing mechanic seems appropriate, and let a flavorful description do the rest. We don’t need to design unique mechanics for each trap. A simple roll combined with a pre-existing effect, and an evocative description is all we need.
