Purpose Built Traps

DnD Trap Theory: Purpose Built Traps

Many times when walking through a dungeon your players will encounter traps. Some of these traps are simple and some of them are elaborate, but they all hinder the hero’s progress in some way or another. One nagging question that sticks out a bit though is why are there traps in the first place. If the trap serves no purpose, you’ll end up having this really weird feeling of video game like rigidity in your game. If the trap exists only because you wanted to put a trap there, it’s not living up to its full potential. The thing that all the best traps have in common is purpose.

What Does it Mean to Have Purpose Built Traps?

Traps can be built for a lot reasons, but if you consider the person who built the trap then you will likely have to think about why they would even take the time to set it up in the first place. Even the most simple traps take time and effort to both construct and conceal.

Just looking at a few examples to start, a dungeon might have traps designed keep people out or keep people in. The traps could be designed to capture, kill, scare, or deter individuals. The traps can be built to be obvious as deterrents or hidden to lure people in. Just thinking through a few of these reasons that traps could be constructed gives you a wild array of options to choose from for constructing your own traps.

In addition to making your traps feel better by considering why you place them, you’ll also get access to many more trap ideas as you think about what you want the trap to accomplish.

Traps Without Purpose

Traps without purpose feel extremely out of place, and that’s because they are. A pit trap in the middle of an empty plain is weird and would likely only confuse your party.

Similarly, you can cause issues by putting the wrong types of traps in your dungeons too. A room that locks your players in and is filled with rust monsters that destroy armor and equipment in a dungeon with no other fights doesn’t make sense. Why were your players being disarmed? Just to make them mad? That seems unlikely and feels bad for your players.

When putting traps in your dungeons or even in the wild, make sure they serve a logical purpose so that your players can feel more connected to the game and get a sense that they are progressing against a purposeful force trying to stop them.

A Closer Look at Purpose Built Traps

Now that we understand why we want to build purpose based traps, let’s take a closer some purposes and traps that could fit those dark goals. There are a lot of reasons to employ a trap, so we’ll break them down into different categories and pull examples for each.

Traps to Keep People Out

Traps that are designed to keep heroes out of a dungeon can accomplish this goal in a lot of ways. The easiest way is by an obvious display of danger. When triggered, these traps don’t even have to hurt the players.

For example, a good deterrent trap would be a hall filled with flame jets that trigger when pressure plates are stepped on. To make this trap a deterrent, simply place the the first pressure plate far before the flame jets. That first step activates them and shows the player just how dangerous the long hallway will be to cross by filling it with fire.

Another type of trap that can be designed to keep players out are chutes or teleports. These are traps that move players around and pop them right out of the dungeon. These can be extremely frustrating because each time one triggers, the heroes would have to start over and avoid all the same traps again to make any progress. A simple linear dungeon full of these traps might take a very long time to get through, but not actually be all that lethal.

Next we have traps that block the path forward. These can be simple, like collapsing pillars, or complicated, like closing stone walls. These types of traps essentially force the heroes to make a decision on which side they want to be stuck on and can serve to keep out those who don’t know what they’re getting into.

The last type of trap that acts to keep players out is the extremely lethal kind. These are like statues that fire disintegration rays. While similar to the first type of trap acting as a deterrent, these don’t pull any punches and murder the first person to walk into them. They are not fun in most games, but they’re worth mentioning since they can serve a purpose in games where you have revival mechanics.

Traps Designed to Keep People In

On the other side of traps that keep people out are traps that are designed to keep people in instead. These traps act as one way passages; move to one side and you can’t move back. These traps also tend to overlap with capture traps that do more than keep people in, but also get them stuck in one spot.

A trap that is designed to keep players in can have a lot of different underlying reasons for doing so. An evil creature my be luring them into their lair to consume them, a lich might be trying move players into an area to drain them of their life essence, or a dungeon may be full of treasure and rather than keep adventurers out, the dungeon adds to its treasure by trapping them with all their gear.

Traps that are one way passages accomplish this by setting up a specific way players have to travel. A narrow tunnel with blades angled in one direction may allow for creatures to climb in only that one direction. A wall trap may spin around and deposit players, but have no way to be spun back the other way. A bridge may collapse after being crossed to prevent any back tracking.

Another way traps can keep players in is by restraining them. These can be grasping vines, snares, bear traps, magnet walls, magical immobilization fields, or monsters with paralysis abilities. The list goes on and on because DnD is very good at providing ways to restrain players.

Traps Meant to Judge People

Traps don’t have to be bad for everyone. Lots of dungeons have traps that are a test of the people who are trying to enter. These traps are only dangerous for those who are “unworthy” of what the dungeon contains.

Traps designed to test your players can involve skill based checks; doors that can only be opened by those who are strong enough, switches that require you to be able to read a certain language to choose the right one, or spikes that only the dexterous can dodge are good examples. Whatever the trap, the goal is to build something that filters out individuals that don’t meet the requirements.

With magic or dungeon engineering there can be even more specific traps. Some traps might trigger based on someone’s alignment, race, or expression. There maybe an arcane eye that watches players as the room tells them jokes and then vaporizes anyone who laughs. That’s a weird trap, but it highlights how easily you can build traps that are designed to filter out certain individuals.

Other traps can be designed to filter out aggression. Magnet traps keep players from bringing metal into certain areas, and anti-magic fields prevent the casting of spells. You could even have oozes that eat everything except for living matter, essentially forcing your party to be completely unequipped to move on in the dungeon.

All of these traps have really strong purposes built into them and make for great thematic set pieces. If you have a weak but ageless being in a temple, it might try to keep out anyone with weapons. If you have weapons that can defeat evil, you’ll want traps that gate evil creatures from entering.

These traps feel really good because they have a lot of purpose and can loudly announce features of your player characters to each other. If one of your characters is a changeling, they’re not getting through that trap that gates monsters. If one of your players is secretly evil, guess who’s not getting that evil slaying sword? The fact that these traps make sense is what makes them so powerful.

Traps that Annoy

Some traps are there just to poke fun at your players. These should be used in the context of the dungeon. A trickster god’s dungeon would be full of these. Beams that make peoples’ weapons rubbery, rooms with reversed gravity, puzzles that force players to embarrass themselves, and so on.

These types of traps are designed to be highly infuriating and should only be used when that is what your story calls for. Trickster dungeons can be fun if everyone understands the reason for their frustration, but if the struggle feels purposeless then your players may have that frustration spill over into the real world and want to stop playing.

Traps to Weaken

Sometimes a trap is designed to use up resources from the players as they progress through the dungeon. These are traps that deal half damage on saves or require the expenditure of materials and spell slots to pass through them. When using these traps your goal isn’t necessarily to kill the players, but the traps are there specifically to make sure when they get to the next part of the dungeon they aren’t at full strength.

Often traps that weaken players are very meta, but they can have in game purposes as well. A clever dungeon architect who can’t afford the biggest and scariest monsters to guard their treasures may design traps that force individuals to fight the monsters they can afford. This is economical dungeon planning at it’s finest! Dungeon residents who intend on fighting adventurers themselves may also favor these kinds of traps. The idea is to prevent a fair fight if possible as the players move forward.

Interestingly, these types of traps can also pull double duty as traps designed to test those who enter; only those who can endure the full length of the dungeon are deemed worthy of its treasures.

A Trap for Every Reason, a Reason for Every Trap

We’ve only just barely scratched the surface here with some of the more common trap types that can be purpose built, but you don’t need to pull from these examples alone. If you sit down and design a dungeon by thinking about what its intended purpose is you’ll be amazed at just how quickly you can come up with a wide range of functional trap ideas. Now that you’re thinking about purpose built traps, go out there and build a dungeon or two!

Happy DMing!

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