Friday, 17 August 2012

Trappery, part four

So far in this series, I’ve pondered:

  • What traps are (and come up with “it depends”)
  • How traps tend to work in games (they go off, or don’t; and cause damage, or don’t)
  • Why traps are unsatisfactory (mechanically dull, narratively dull, don’t make sense)
  • What the point is of having traps in real life (alarm, deter invasion, damage morale, covert attack, protect the unguardable)
  • How I’d like traps to affect my game (exciting narrow escapes, interesting problem-solving)
  • Useful functions that traps could perform in RPGs (creating a sense of danger, testing PC competence, encouraging caution, validating playstyles, creating decision points, triggering encounters, complicating encounters, challenging player ingenuity)
  • Possible stages of interaction with a trap (spot, identify, neutralise, survive, aftermath)

Last time I suggested taking a look at trap design, both in reality and in game-mechanical terms. That seems like a good way to take things. Let’s start with real trap design. I’m going to be assuming a roughly real-life setting, but these ideas should be mostly applicable to fantastical settings, and ‘technology’ and ‘magic’ are largely interchangeable.

by Wizards of the Coast

Aspects of Trap Design


A good starting point is the lethality of traps. In most societies, premeditated killing is illegal even if it’s allowed in immediate self defence, so most legal traps cannot be lethal. Ordinary citizens usually have relatively safe lives, so are reluctant to endanger themselves by having security systems that could kill or maim them. There are also concerns about injury to unexpected callers, like paramedics or firefighters.

The military are a notable exception, as they tend to take a harder line on lethal force, acceptable risks and fatal accidents. If someone breaks the rules or makes a silly mistake, and gets themselves killed, that’s unfortunate but not catastrophic. The magnitude of the threats they face outweighs concerns of absolute safety and nonviolence. Xenophobic societies that despise outsiders may also not care about them getting hurt unnecessarily, though these generally have more concern for their own members than the average military.

The other main exception is anyone operating outside the law, be it hardened criminals, powerful individuals, repressive security forces, or wilderness dwellers. These are not worried about legal consequences. Again, the safer the trapper’s own lifestyle, the less likely they are to risk using lethal traps in case of accidents, though leaders may order minions to place traps where they themselves aren’t at risk.

In short, if you’re a law-abiding citizen or company in a peaceful society, your traps will usually be non-lethal, and often non-violent. The more violent your ordinary lifestyle is, the more violent your traps are likely to be. Megacorporations in dystopian futures may set nerve gas traps with impunity, knowing that they make the law, just as gun-toting pioneers on frontier planets lay mantraps and dig spiked pits. Finally, the lethality of traps is weighed up against the magnitude of threats they are defending against, or at least believed to defend against.


A second issue is the impact of traps on the trapper’s own activities. A trap should not create more problems than it solves. Military bases, palaces or nuclear plants will accept a lot of inconvenience because of the risk posed by security breaches, so you’re iris-scanned at every door, there’s tight monitoring of email and net access, and queuing through scanners and random searches on the way in and out . Companies with data or equipment to protect demand ID swipe-in, and the server room locks down if you mistype the password. Spies and organised criminals may take elaborate precautions with passwords, rendezvous times, and checking for weapons or bugs. Shops trap expensive goods with dye sprays. Jewellers’ shops are at considerable risk for their size, so they have reinforced shutters, cameras, detectors, locked cases and .

For ordinary citizens or small businesses, the amount of activating, deactivating, locking, recharging, feeding and hazard-avoiding they can be bothered with depends on how seriously they are worried about security. Most of us are lazy and pragmatic, and locking up plus setting a burglar alarm is the most we want to faff with. That’s enough to deter opportunists, and any really professional burglars can probably evade any security measures we could afford. Setting pit traps or poisoning doorknobs requires time and effort, and we have to remember about them when we come back in, warn any visitors not to rush in after us, get the pit cover from the cupboard and replace it, painstakingly wipe off the poison and dispose of the cloth, and add ‘contact poison’ to the shopping list for tomorrow because we’re running low. That stuff ain’t cheap, either. By time we’re finished, our date is soaked to the skin from waiting outside in the rain, and the ice-cream has melted. Then we remember we forgot to shut the hall door, and the neighbour’s cat we’ve been looking after has a cute trick of opening doorknobs. I mean, had.

Traps are even more inconvenient once they trigger: alarms waking neighbours, people getting trapped in pits or blasted with tear gas, and potentially both property damage and dead bodies to account for, not to mention clearing up afterwards and filling in the inevitable forms. People won’t tolerate that much inconvenience unless it saves them from greater problems. Broadly speaking, then, people in low-risk situations tend to have high-threshold triggers to avoid annoying false alarms. In contrast, people with serious concerns about security will have sensitive triggers; they’re willing to ensure the hassle of false positives for the sake of never missing a real intrusion. The motion detector in the armoury is a lot jumpier than the one in your living room.

In summary, the sensitivity of triggers and the difficulty of avoiding them tends to correspond roughly to the risk of intrusion and the amount of harm intrusion could cause.


The problem with most forms of security, including traps, is the people. The ideal form of security, as certain emperors surmised, involves the guarded object being hidden in an impregnable chamber somewhere utterly inaccessible, guarded with an array of utterly impassable traps; and then to eliminate not only the genius who designed the chamber, the genius who designed the traps, the workers who built both and everyone who knows the location of the object, but also every single person who knows it even exists and every piece of evidence that mentions it.

from Wikimedia Commons

Unfortunately (unless you’re a genius engineer), this is generally not feasible. Most of the things that need guarding are only valuable because they’re useful, which means people need access to them. That’s true for powerful tomes, crowns, financial data, shop stock, munitions, money, homes, commercial secrets and personal possessions. There are three main issues here:

  1. how public the protected area is;
  2. the people who need to safely pass the trap;
  3. the people who need to activate, deactivate, reset and maintain the trap

In a public area, it’s hard to justify using dangerous traps or those that trigger indiscriminately, as there’s a good chance of false positives, collateral damage and other inconveniences. Even despots won’t put fire traps in the city square; they keep them behind walls, guards or other obstacles that create a secure area. Similarly, you don’t want the ever-popular laser sensors installed outside the loos where legitimate employees will be setting them off constantly; you put them in the vault.

If a lot of people need access past the trap, you need an easy and reliable method to do so. This might involve ID readers, keys, passwords or knowing where the pressure plate is. Information is harder to lose, leave behind or steal than keys, but easier to pass on without anyone knowing and possible to forget; you’re more likely to mistype a password or step on the wrong flagstone than your ID is to malfunction. A large number of people means more chance of mistakes (and therefore false alarms), particularly if the pool of people changes a lot, so very deadly traps become problematic. A large and changing pool also carries a greater risk of security breaches, and can make some pass methods expensive. In general, information-based passes are more suitable for small groups of trusted individuals who won’t gossip, while larger groups call for personalised passes like ID checks or even biometrics that check if the visitor is who they’re claiming to be. Finally, the access method needs to be suitable for its users: some types will remember passwords and treat ID with great care; others will forget everything, gossip in the pub and lose their keys every weekend.

Most of the above applies to trap supervisors as well, but they have additional power and will know more about how it works, while visitors may just know it exists.

In short, a trap in an area exposed to innocent bystanders is likely to be less dangerous and more difficult to trigger. The more people who bypass the trap and the greater their turnover, the more forgiving the trap should be, to allow for mistakes. Information passes work well for small trusted groups, but larger groups call for more personalised methods.


At some point, traps will call for your attention, for one of two reasons. The first is simple maintenance: traps need repairing, oiling, testing and so on, whether they’ve been triggered or not. The second is that once a trap’s been triggered, it will generally need resetting, reloading, refuelling or otherwise putting back in functioning condition. You may also need to repair damage caused by the trap, conceal the trap again, clean up any bodies, or extract anyone captured alive. If the traps don’t immediately kill intruders, then unless you respond to check out the area there’s a real chance they’ll manage to escape, or even find a way past and nick your stuff. How easy any of this is depends on the environment of the trap, and its location. A trap buried five miles underground in a dark, gas-filled tomb littered with other deadly traps is a trickier proposition than your burglar alarm. A pit trap or ensnaring charm is useful if you inspect the room regularly, but otherwise you may just find a few dangling ropes, the hacked-up remains of some vines, and a big empty space in your treasury. Similarly, an alarm is no use if there’s nobody to hear it.

In short, the circumstances of the trap will affect what traps are useful. If the area remains accessible to trappers, then non-lethal traps, deterrents, and high- maintenance traps are viable options. If it’s dangerous, remote or sealed off, then clever intruders will have plenty of time to find ways around obvious traps, and to escape from non-lethal traps they do set off; there’s also a good chance that traps will stop working over time. As a result, these situations are better suited to either impassable defences, or concealed traps that are instantly fatal. They also call for very reliable traps, since there’s nobody to notice breakdowns, which either means simple traps that can’t easily malfunction, or very robust and probably expensive technology.

What's Your Trap?

If you’re designing a trap, there’s a few questions you should ask yourself based on the points above:

  • What’s the main objective of the trap?
  • Who or what are the targets of the trap?
  • Who uses the area, and who has authority to bypass or deactivate the trap?
  • How serious is the threat you’re guarding against?
  • How dangerous is your everyday life?
  • Are you military, official, commercial, criminal or a private citizen?
  • What sort of budget and resources are available?
  • How easily can you maintain or inspect the trap?

That seems like plenty to be going on with for now, and this is a long post now, so I’ll leave things there until next time. Next time on Trappery (unless I change my mind): deriving practical details of traps from these basic points.


  1. If only Umbrella Corporation had read your article there'd be far fewer worker's comp claims filed in the courts.

    1. Dystopian megacorps are a little neglectful of their responsibilities sometimes.

  2. Also, MORE trappalicious articles!

    Looking forward to the next one.