Traps in some game systems are standalone elements. However, I consider them a hazard if they factor into a combat in any way. Encounters without combat that just have traps in them I would consider hazardous for your health, but not a combat hazard.
Traps have been around RPGs since day one. In my first D&D session in grade 5 we were playing Keep on the Borderlands and my rogue got nailed by a trap in the kobold lair. 5 points of damage! I begged the cleric for healing and continued onward, but more cautiously. And by more cautiously, I mean everyone else lead from that point on while I guarded the rear.
Traps on the battlefield are a ton of fun. They heighten drama, add risk, and provide new options to combatants. They should be more than just a damage dice roll. Minor traps can harass, impact movement (pun not intended), cause hesitation. Traps can change the course of battle.
A third foe
In typical battles there are two sides. Traps create a new enemy, usually unaligned. They open another front for foes to defend or strategise against. Consider traps as a third foe, or x+1 if there are multiple factions in a battle. This not only helps with encounter balancing, but ensures you champion the traps well in your planning – traps added as an afterthought often feel patched-on or are underperformers.
Envision the trap in battle
This is a fluffy tip but oh so important, and oft neglected. How do you see the trap working in the battle? What contribution do you envision it making? How do you imagine it will affect gameplay and make the combat more fun and interesting?
Busy game masters will be prone to just selecting a trap and placing it on the encounter map. This is fine some of the time. But you should celebrate traps as strange, dangerous, and unusual combat elements. Make them special.
Unexpectedly triggered traps are wonderful in combats. For example, you’ve heard of land minds? What about magic mines that detonate if a certain school of magic is cast? Proximity triggers work well too, especially if there are specific triggers so it becomes a bit of a puzzle.
Traps in unexpected locations are always good for a table laugh, such as traps to the sides of doors, traps in front of fake glowing objects, trapped treasure, and so on. Portable traps can help you work out a lot of inconsistency issues that pop up with surprise locations, such as when arming areas already swept by the party or locations dangerous to everyday life.
One side or the other can control various settings on the trap to provide tactical combat advantage. Perhaps a trap can be aimed, suppressed, disabled, delayed or embiggened.
The first trap merely starts a sequence with deadly consequences. The puff of air is shrugged off by the barbarian who watches in fascination as the air pushes a round rock that rolls over to a switch that cuts a rope which scuttles across the floor up to the falling ceiling block….
Shock and awe
Traps can contribute more than blood cell count on paving stones. They can release new hazards, such as smoke or glue, or loud noises to attract more combatants, or a massive magnet effect that slows all metal armoured foes.
At some point during encounter design or preparation, envision how the combat will run and what role the trap has in it. Likely you will spot deficiencies and opportunities you’ll still have time to tweak for.
For example, with their fly ability PCs might use air superiority to make battles against land-bound foes easier than expected, and low ceilings is getting tired in the game. Perhaps some airborne invisible mines will make the PCs cautious for this combat and the next few too.
Placement is key
Some spots are better than others when placing a trap on the battlemat. Think of it like a chess game or tactical board game. If X happens then what? If Y happens in response, then what?
Some of the many factors to consider:
- Where will the PCs enter or be placed on the battlefield?
- Where will the foes enter or be placed?
- What likely movement routes will be taken by either side?
- What battlefield features will draw combatants to inspect, engage with, or move toward?
- Do the PCs tend to spread out or clump together?
- What are the usual attack modes of the PCs? (i.e. potential trap trigger conditions)
- Who is likely to win initiative?
- How fast can the PCs move?
A lot depends on the nature of the trap. Once you have a trap selected, look for its strengths and weaknesses. And untriggered trap in combat is such an unfortunate waste. Look at what the trap needs for it to be triggered, the type and nature of damage it does, and what might increase its chances of success.
Be creative with effects
Look at every condition and damage type in your game and build traps for them. Same with spells and strange effects. Look at the special abilities of the PCs, equipment, and magic items. Apply the most interesting effects to traps.
For example, a trap that emits concussive bursts, dazing friend and foe alike, is much more fun to play than one that merely does 1d6 damage. A trap that causes allies to attack each other, or forces combatants to flee in a random direction, or makes victims attack by grapple makes combats memorable.
Do not forget about area effects. Smoke bombs, noise suppressors, or bursts of substances can catch everyone off guard, or at least affect multiple victims for greater combat chaos. A trap that causes a wave of magical effect to blow through the battlefield will get everyone excited, as would a tall building forced to collapse or long chain whip that whirls across a huge radius.
Make some traps obvious
Not every trap needs to be invisible or catch combatants by surprise. Sometimes the obvious ones are the most entertaining. Either one or both sides avoids the area of the trap, which could have consequences, or foes try to figure out how to use the trap against each other, or while the fighters fight, the rogues and bards get some investigation gameplay in.
Why is the battlefield trapped?
Be sure to make the situation believable. Justify the trap’s existence. “Previous owners” is often a good answer. Portable traps allow lots of utility. A large expense account is another plausible answer.
Watch out for tricky answers. You don’t want to spend much time on trap backstories. If you see your answer getting complex, that’s a flag to simplify your explanation about why the trap came to exist where it is. Another, er, trap, is having to create layers of new game elements to support your rationale.
“Just because” is a good answer too, but I don’t want you to get cornered by clever players who choose to investigate the trap looking for details, or who find a logical flaw with the trap selection or placement.
Hopefully your battle traps become part of post-session stories and the campaign’s lore. They are so versatile and offer so many options for changing combat strategy, atmosphere, or difficulty.
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