A Walk in the Dark A look in to the mind of an RPG designer



Traps in 13th Age

As I think I've mentioned before, I've fallen in love with 13th Age... so much so that I have decided to convert my uber-campaign The Coming Dark entirely from Pathfinder to 13th Age. It's somewhat of a daunting task; in retrospect, I probably should just have written it from scratch, simply because that several design philosophies differ between the system.

In working with 13th Age, I noticed that there are several aspects that are lacking from the core ruleset: curses, diseases, poisons, detailed trap/hazard implementation, etc... All of which I need, at least if I choose to stick with the module as it has been designed for Pathfinder.

The following is my attempt to explain how I am going to implement some of these things in 13th Age. Let's start with the most commonly used...


The 13th Age book does not give a whole lot of emphasis on traps. To be specific, they're really only talked on one page (page 185) and are referred to as going "out of style". Frankly, I disagree with that; I think traps are somewhat of a necessity, especially if you consider the term "trap" abstract. Every trap isn't an acid jet or a 10' pit, after all... and there are several things that fall under the trap rules that just can't be lumped in to what the text describes as a "trap".

In addition to that, the text provides the "impromptu damage" table that doesn't scale with the party. A "normal adventurer" trap is much easier to a 3rd level party because the +5 attack roll is theoretically unchanged. And the second you take a step in to Champion levels that attack roll rockets up to +10.

What I have chosen to do in some cases is to treat some aspects of the trap as it is a monster. This includes handling attack rolls, initaitive, damage, and even hit points (when applicable) so that they do in fact level with the party.

Here's the guidelines I am using... In my initial example, for argument's sake, I'm going to design a trap that causes a cave-in.

Type of trap: First off, there are two types of traps: "mechanical" and "magical". "Mechanical" traps involve some physical aspect that isn't powered by raw magic - be it a pit, a large stone block, an acid jet, etc... - and as such require physical interaction to disarm them since they have no magic to be disspelled. "Magic" traps are created with raw, arcane power and as such are more likely to be disspelled with a counterspell than to be manually manipulated. A rogue trying to use thieves' tools on a magical trap is probably in for a nasty surprise since the trap isn't designed for that to be effective.

There are also other types of traps or hazards, such as "obstacle" or "terrain", which would inherently define how the trap is dealt with. We'll get to tat later.

Example: Our cave-in is clearly mechanical; no magic involved.

Trap Level: This is in parallel to what 4th Edition does. The trap's level defines its difficulty, its attack roll, its damage, etc... Traps can also be large, double-strength or triple-strength depending on their complexity and how threatening they are.

This also factors in to encounter balance; if the trap is active while an encounter is taking place around it, in terms of encounter balance the trap is treated as a monster of equal level and difficulty.

Example: Our cave-in trap is designed for low level but it's big and menacing, so we'll keep it simple and define it as a "Triple-strength 1st level trap [MECHANICAL]"

Initiative: If the trap requires some sort of initiative, such as traps that remain active and repeatedly attack the party, you can use the same guidelines as monsters, which is "initiative adjustment + level".

For mechanical traps, generally the initiative adjustment should be low, like +0 to +2. Magical traps, by nature, should have notably higher initiative counts since their reaction is driven by arcane magic, so I'd say put these at +2 to +4 if not more.

Example: Our cave-in is a one shot - it happens and that's the end of it - so no initiative applies.

Detect DCs: You can use the same guidelines as normal DCs in the game; DC 15/20/25 for Adventurer level depending on whether the trap is easy, normal, or hard to detect.

If the players fail to detect a trap that has an initiative count, the trap should either get a surprise round or its initiative count should end up being higher. One easy solution is to "take 20" for the trap's initiative roll.

As far as who can detect what kind of trap, preference should be given to the right classes. Rogues excel at detecting mechanical traps, so you may want to consider giving them a small bonus (as if it was a background, say +3) to the detect roll. If the trap is magical, arcane spellcasters should get a like bonus. You can even go as far as to give rangers a bonus to detecting terrain hazards. Use your discretion; if the PCs give a convincing argument, give them the benefit of a doubt.

Disarm DC: Same guidelines as above, but how the trap is actually disarmed is up to your interpretation. Rogues excel at dealing which mechanical traps, while spellcasters can channel arcane energy to dispel or neutralize magical traps. Some traps or hazards, like terrain hazards, can't simply be disarmed and have to be dealt with via conventional means.

In some cases it may be possible to simply circumvent a trap without actually "disarming" it. If players detect and trigger a 10' deep pit to open up in front of them without falling in, finding a way over it now that they know it's there may not require a skill check at all.

If the player fails the check to disarm the trap, you can either explicitly specify what will happen or you can use your judgment. You can also give the players a cushion for failure; for example, if the DC is 20, if the player rolls a 19 he might be able to get away with not triggering the trap. In these cases, you can specify a triggering threshold, such as "<15 triggers", so only if they fail to meet a DC 15 will the trap actually spring.

Note that if the player fails the check but doesn't spring the trap, he can try again, at least until he succeeds or the trap is sprung.

Traps that are "obstacles" or "terrain" may not have a means by which they can be disarmed; they're just there, a permanent fixture that can't be gotten rid of.

Example: Our cave-in should be fairly difficult to detect by the average PC, so let's leave it at a DC 20. As a DM, I would consider giving bonuses to dwarves or anyone that can detect irregularities in the stone work, assuming of course the PCs provide a convincing argument for such a bonus.

To disarm the cave-in is another matter entirely. First of all, if the hazard is detected the party can simply step around it or go another way, neither option of which would require a skill check. If the players choose to do something about it, such as brace it or prevent the trigger from being set off, it may require a roll if you so desire; in this case I'd set it at a DC 15 or DC 20. I would also grant the same bonuses I did in the detect above, such as giving dwarves a +3. Let's go with a DC 20 for argument's sake.

If the PC rolls a 15 or lower on the check, the cave-in should begin.

So our block reads "Detect: DC 20" and "Disarm: DC 20, <16 triggers".

Trigger: Most traps aren't active all the time; something sets them off. When the trigger condition happens, the trap will either enter the initiative order (if it has initiative) or simply attack.

Example: Our trap should trigger when the party proceeds down the cave tunnel. So, put simply, the block should read "Trigger: walking down the tunnel" and leave the rest to DM discretion.

Hit Points and Defenses: If the trap is a physical entity - a dragon's head that spits fire, a sharp blade on a swinging pendulum, a barrier of arcane force, etc... - it should have some degree of hit points. For this I would use the guidelines set forth in the "DIY monsters" section of the core manual, possibly choosing double or triple-strength characters.

In non-combat situations, it may not be necessary to track hit points at all. If the fire-breathing dragon's head is not threatening the party and the party is trying to damage it from a safe distance away, you can safely assume that the party will eventually cause enough damage to destroy it. Only when the party is in imminent danger, and they are under a clock to stop the trap before things get much worse, should you even bother with tracking HP. The same goes for the trap's defenses: if the party is out of range and unthreatened, unless there is a possible risk to the party there isn't a need to make an attack roll every time a PC takes a shot at it. Just assume that, eventually, they'll hit it enough to break it.

If you determine you need hit points, you will probably need defenses. Except for the really unusual 1% (such as traps that have a spiritual presence), traps do not have a Mental Defense and are immune to any sort of psychic attack. Most traps, specifically mechanical traps that are immobile, should have a relatively low AC compared to their PD, so much so that as a DM you might even consider attacks that target AC to always hit.

Example: The cave-in doesn't need any hit points to speak of. You can assume that if it gets attacked once it will trigger but that's not something that needs documenting, much less an attack roll.

Attack Type: One way or another, the trap's going to attack. It may attack once, it may attack repeatedly, and it may even have multiple forms of attack, but it's gotta do something.

As a basis I'm using the standard guidelines for monsters: Level+5 for the attack roll. Depending on the nature of the trap it will attack AC, Physical Defense or Mental Defense.

Depending on the nature of the attack you also have to decide:

  • Whether it's a melee, ranged or "close" attack.
  • How many targets it can affect, and whether those targets are "nearby" or "far".

Example: Our cave-in, being level 1, gets a +6 vs PD close attack that targets all nearby creatures.

Attack Damage: This is where it gets tricky... If the trap is in an area where there is an active encounter, its damage should be on par with a monster of equal level. In that case you can choose to use the static "strike damage" value in te DIY tables as a basis.

If the trap is outside of an encounter, and especially if it's a single use trap (like our cave-in), the damage should be considerably higher. This could arguably be covered by using the double-strength or triple-strength numbers. But even then, static numbers are averages by definition, so you might want to roll actual dice. In this case, use the table's "strike damage" as the average die roll and base your die pool on that.

The trap, like monsters, could also have secondary effects and attacks for special rolls, such as effects that trigger on "natural 20", "natural even hit/miss", etc... If you're doing something Fourthcore-like, you may even consider something like "Natural 20: Death".

Magical traps could be significantly more complex, similar in what they can do to wizard or sorcerer spells. Be as creative as you want; magical traps are magnificently lethal by design, and they should be extremely complex-looking and dramatic.

Example: Our cave-in is a pile of really big rocks crashing down on the party, so it's gonna hurt. That being said, I consider it a triple-strength monster, so the strike damage is 15, which is actually the average of 4d6 s0 let's go with that for our damage.

If the trap misses, it still might hurt a bit so let's add an additional condition: "Natural even miss: Half damage".

Additional effects: Traps may have additional effects, "nastier specials" or other features just like monsters do. If you want the trap to be either persistently annoying or downright lethal if a PC blunders in to it, you can choose to add a lot more complexity to it for dramatic effect.

Example: Rocks fall. There really isn't much room for creativity in this one.

Given all that, we now have our stat block...


That about covers traps, I think. I'm sure I'm missing something, but it'll come to me some other day. Maybe soon I can provide some more examples from The Coming Dark.