What makes a good trap?
It should follow good OSR principles (similar to the obstacles post I wrote way back).
- No obvious solution.
- Multiple possible solutions.
- Solution depends on common sense (rather than system mastery).
- No specific tool required (no McGuffin, no singular spell, etc).
What is a trap?
A trap can be obvious, such as an open pit. With obvious traps, the puzzle becomes how to best get across the trap. Traps don't have to be difficult. Easy traps can be fun, too. AND easy traps can become weapons that you later use against monsters in the dungeon.
Obvious traps are probably the hardest to write, and the most fun. They kind of blur the line between obstacle, puzzle, and trap. An obvious trap needs to have (a) a reason to engage, (b) a visible mechanism, and optionally (c) an explicit risk.
A trap can be surprising, like a subtle pressure plate. With subtle traps (where the PC is likely to stumble into it) make sure that you give the player a chance to react before the trap goes off. We want to give the players interesting choices to make, not just tax their HP.
A boulder rolling towards you is good. You still have options. Compared to. . .
A subtle pit trap in a random location sucks. It sucks because the "solution" to them is to spend your time tapping on the floor with a pole, or pouring out water and seeing if it seeps between the stones. (I know there is a whole branch of old-school play that enjoys this style of play, but it's never appealed to me, since I believe that there are more interesting ways to challenge players.)
Where should subtle traps be hidden?
Please don't hide them willy-nilly. Putting a pit trap in the middle of a well-traveled corridor threatens verisimilitude (since aren't orc patrols passing over it every thirty minutes?)
Place traps in logical places. A kitchen cabinet is probably not going to be trapped, but the chest in the shaman's room probably is.
If you are going to hide damaging traps, try to build up to them. Telegraph the possibility before the traps appear. Before you have complicated double pit traps and slides, it's good to have a room with a small pit trap (to inform players that hidden pit traps exist here). Or better yet, a room with a broken (exposed) pit trap.
You don't have to telegraph the danger, just the mechanism.
For example: a lever might open a hole in the ceiling, dumping spiders down onto whoever is below. A smart party will pull the lever with a rope lasso from 20' away.
This is a good trap. A player who dies from spider bites will (hopefully) sigh and say "I guess I deserved that.".
That's what you want from a trap.
Not all of these are technically traps. Some are just interesting dungeon features.
- Wall of fire.
- Zone of unconsciousness.
- Climb a diagonal shaft, rotating.
- Crush hallway. Find a way to survive the crush, or at least move really, really quickly.
- Portcullis that slams shut to split the party. You can reunite 1-2 rooms away (don't split the party for too long).
- Obvious pit trap. The correct path is hidden at the bottom of the pit.
- Insanely hot hallway (or room where you have to perform some activity). Anyone trying to sprint through it unprotected is probably going to burn their feet and die. Things that reduce damage: being soaking wet, air circulation, walking/standing on soggy leather.
- Subtle pressure plate. The trap triggers when weight is taken off the plate.
- As above, except there are several pressure plates in a row.
- Goblin barricade staffed by several bow-wielding goblins.
- Obvious trigger: taking the sword off the pedestal. Two copper spears shoot out of the wall, impaling an incautious explorer. A round later, lightning begins to arc between the spears. A round later, the room begins to fill with water.
- Poisonous gas seeps from a crack in the wall.
- Lake of acid. Get to the island.
- A dripping wet door. Opening it floods the room with ancient, rancid water and 3 zombie sharks.
- Lock that can only be opened at a certain minute each day. Adjacent, a lock that can only be opened at a certain minute each week. Adjacent, a lock that can only be opened at a certain minute each year.
- Archway. Anyone who passes through it is transposed with a ghoul in a nearby room.
- Climb a frictionless wall. (Have fun collecting large furniture. Shitty tables are treasure now.)
- The floor of this room is laminated with symbols of disintegration. If a symbol is touched, all non-stone material in the room will take 3d6 Con damage each turn. In the room, an (unsupported) pedestal with a stone McGuffin on top. In the ceiling: spiders and spiderwebs.
- Everything appears distorted in the mirror. Humans appear to be orcs, swords appear to be hammers, etc. The trick is to notice that the pen appears to be a key, and the mouse skull appears to be lock. Inserting one into the other will cause the door to open.
- Huge wooden bowl, lined with thin, insoluble gold foil. Filled with horrible, fuming acid.
- The magic stein can only be carried by someone who is colossally, totally drunk. They have to carry themselves--no one else can help them.
- Carry a baby out of the dungeon. No, carry ten babies.
- When the lid of the sarcophagus is placed back on top, the bottom of the sarcophagus opens.
- Sign says "teleporter" but it's really just a big blender.
- The dragon is sleeping! Steal things quietly. (Common sense: it's quieter to carry a chest away than it is to open it, a sack of coins is guaranteed to clink, etc).
- As above, except some goblins just showed up. They want to kill you quietly, but if the dragon wakes up, you're all probably going to die.
- Crossing an underwater lagoon. Hope you brought a canoe. Of course something attacks during the crossing. A fast boat can escape it, a floating table is easily capsized.
- Functional teleport brings organic material to one place, and inorganic material to another. Allow teleported people to communicate this (possibly by shouting, roll for random encounter) so they can make a more informed decision. An incipient threat hastens plans.
- The door can only be opened in your dreams. If you open it in your dreams, you can pass through it in real life. While your body sleeps on the altar, it is inhabited by the spirit of an ancient wizard.
- Before you can run through them, you need to observe the swinging pendulums to determine their pattern. Anyone observing the pendulums is hypnotized by them, staggers safely through them, and begins to self-mutilate by dancing in the middle of all of them (1d3 damage per turn).