How can I secretly notate which squares on a combat map are traps?

Question

The party has ventured underground. One of the civilizations where they are is kobolds. I (GM) went trigger-happy with pit traps, falling block traps, and a couple of others. The kobolds have one path which leads to their enemies and they've set it up so that there's a fairly specific winding path through them. I'm going with the idea that instead of passwords, they know the safe routes.

There's a problem. While this is cool in theory, my plan fell apart when I saw just how many traps are on the map. I imagine myself checking and double-checking the moves players make every round. Since I'm not keen on the idea of sluggish combats I have concerns about how to execute these fights with the traps. It'd be particularly embarrassing if the kobolds walked over a trap space, themselves.

Before this fight, the party will have fought kobolds but will not have been in the 'minefield.'

How can I keep note on which squares are trapped on the grid, instead of having to continually switch between their map and mine?

Answer 1

How do the Kobolds remember which parts are trapped?

Basically, this answer is about weaving the Kobold's own marking system into the narrative. It does assume you draw your own maps and don't use Dungeon Tiles or anything.

Obtain 6 or so pretty looking symbols (they don't need to have meaning, but if they look Draconic it's bonus awesome) Mark every square of the map with one of them. In the narrative, explain that the Kobolds did just that; they covered all the floors with all sorts of markings. For each room, assign 2 symbols to mean "trap" and the others to do nothing. Vary the symbols per room.

This will clearly signal to the players "this room is trapped", but then the word Kobold is basically a synonym for "traps" anyway, so that's okay. It will keep your players attention strongly on the traps, they will try to figure it out by watching Kobold movement (which is good! traps exist in the narrative to be interacted with) and will mostly stumble right into a trap in room 2 before they realise that the Kobolds vary which symbols mean trap in every room.

You could even tie a meaning to each symbol (in Draconic) and explain the words to players who speak it, and then have the chosen symbols make sense per room. Since Kobolds employ deadly traps in their home, they need a system to keep down their own losses, and that has to be simply enough to teach to their kids while still being confusing enough that confound and/or kill enemies.

To tie it even stronger into the narrative, include a room that the Kobolds use for training their young (probably one with few or no Kobolds in it, since they know it's less hurtful) where the traps just drop a bucket of water on their heads or launch sticky paper at them.

And maybe in the newest room, the Kobolds haven't had time to place traps yet, but they did place the markings. Your players will be properly trained by this point to move very carefully, figure out the system, and probably be amused when they realise the Kobolds have trained them like Pavlov's dogs to avoid certain squares, even if they don't do anything. (If they are trained so well they never trigger any, make sure they find a scrap of paper later that has instructions on which traps should go where that makes it clear none of them have been installed yet. Remember: if you don't tell them, it doesn't exist.)

(Regarding the last part, I once trapped my players in a room inside the Temple of the God of Theater, by giving them a huge grid full of letters whose only effect was that certain letters made the floating balls of electricity in the corners light up ominously. They were told that the room was "very dangerous and none had ever traversed it". It took them an hour to figure out they were being played and they loved it.)

Answer 2

This answer basically trades significant amounts of out-of-game prep-time in order to save in-game play-time. For a variety of reasons (but mostly because it’s horribly tedious), I have only used it a few times.

The idea is to mark traps on the grid, and then cut up post-it notes and cover the markings. Have to make sure you have sufficiently-opaque post-it notes, and it’s really time-consuming and tedious to prepare, so I have also tried just using coins – the weight keeps them in place well enough as long as the environment isn’t too shaky, and they’re about the right size, fairly uniform, and reasonably easy to get in decent quantity (don’t try it on a wobbly table though).

Anyway, when anyone moves, the coverings are removed. You can leave coverings on the squares that enemies move through, but if the PCs can see them moving, I find it easiest to just assume the PCs can remember the safe spots; YMMV. Anyway, trap-filled areas require moving square-by-square¹ anyway, so you can just remove coverings as each square is entered, springing a revealed trap if there is one.

The benefits are that this preserves the information if you have to end the session mid-combat (and reminds players of what the characters learned twelve seconds ago when it’s been two weeks for the players), it’s relatively quick to see whether or not a trap was in any given location, and it does a decent job of providing a little moment of tension as you wait to see if a given square is a trap. You can also not cover every square, if you want to make it clear that some areas couldn’t (reasonably) be hiding a trap, while others could. Maybe the road is safe, but who knows about the bushes?

1. ^{Which is just one of many reasons why I hate traps and rarely use them; moving square-by-square is really slow and allowing people to move more naturally but then having to stop the action to ask “wait, what path did you use?” is even worse.}

Answer 3

I did something like this for a specific large passage in a dungeon in my game, the solution that worked well for me was to have trap placement dictated by a hidden pattern

At first it might seem like this would be too obvious, but you'd be surprised how difficult it is to work out a pattern when you don't even know if there is a pattern in the first place, especially in the middle of play and with imperfect information.

This isn't quite the pattern I used, but if you imagine a setup where each trap has another trap every 3 squares horizontally and two squares vertically you can end up with something like this:

|T   T|
|  T  |
|T   T|
|  T  | 
|T   T|
|  T   =========
|T   T   T   T
|  T   T   T   T             
|T   T   T   T  
 ===============

That's a lot of traps! However, it's also super easy to infer the position of any additional trap as well as knowing safe places to walk. So long as you know the position of one or two traps, you can simply count out by twos and threes quickly in your head to see if anything happened. You can even place a few visibly on the map as triggered traps both to make the players nervous and to act as markers to help you figure out the others.

Now, when I did something akin to this one the players figured it out a little after the bend in the level, which is what I wanted (the actual path went on much farther and they were in combat while on it which added an extra thing to keep track of). For your situation it's vitally important that you decide how decipherable you want your kobold trap system to be.

• If you want the players to be able to have a chance to figure it out then you're going to want a frequently repeating pattern with high visibility when a trap is triggered so they have as much information to work off of as possible, it will seem much more obvious to you than it will to them due to you already knowing the answer but they should figure it out after a few iterations
• If you want them to have to pay attention to the kobolds movement to know where to move then you're going to want a non-repeating pattern, or one that doesn't repeat until after the section they have to navigate. You can also use a pattern with just a few gotchas thrown in to feed the players bad information as then you only have to actually note the gotchas (and you can still use terrain features as reference points).
• If you don't want the players to figure it out, then just don't bother to mark the traps at all and use DM Fiat on where they are triggered. If someone calls you out due to a kobold using a square that is suddenly a trap, just point out that they (probably) weigh a lot more, or the kobold knew how to step over it without triggering it.

Overall you have a lot of options, but a pattern will help you keep track with little to no marks or notes.

Answer 4

I've used a "Minesweeper" strategy for this to good effect. To use @Lunin's example:

|T 3 T|
|  T  |
|T 4 T|
|  T  | 
|T 4 T|
|  T   =========
|T 4 T   T   T
|  T 4 T 4 T 4 T             
|T 3 T   T   T  
 ===============

Instead of the numbers, I drew a star-like pattern with a point pointing toward a trap (and a dot in the center if that square was trapped). That way, I could mark a 3x3 space with just one square.

My particular situation was a bit easier; the encounter was in a room that had a mosaic floor, so it was easy enough to convince players that the markings on the battle mat just showed the decoration, and I could easily throw in meaningless marks as well. I also wanted them to figure out the system relatively easily after tripping a couple of traps. For what it's worth, it did take them about three traps to start figuring it out.

Answer 5

A very simple approach, which I'm surprised no one has suggested yet, is to simply not decide in advance.

Say there are 100 squares, and you want to have 10 traps. So whenever a PC moves to a square they have not been on before, roll a d20, and on a 1 or 2 they stepped on a trap. Problem solved!

Or say there are 5 pit traps and 10 spike traps. Now 1 or 2 are spike traps, and if you rolled a 3 they step on a pit trap. See where I'm going with this?

That way, all you have to mark are the spaces known to be safe - which you can even have the players help you with! When a kobold moves, just don't roll for it, and assume wherever it steps is safe.

That way, you get the result you want, combat stays fast, and you look like a genius for memorizing the whole map.

Answer 6

Not trying to sidestep your question, but I think your goal can be accomplished without tracking each square.

1. Track "Zones"
   In your notes, you could identify areas of the map that contain certain kinds of traps without specifying where exactly on the grid the trap is. When someone passes through a zone, just assign the trap a specific square. This might not preserve the fully labyrinthine feeling you want, but it is easier.

2. GM Magic
   A much better approach might be not to pre-assign traps to any spaces. A single square is typically 5 ft. by 5 ft. In that much space, a careful person might be able to tread without spring a trap. Perhaps the kobolds know how to do this? Alternatively, you might let the kobolds travel a strangely indirect path to the PCs or fail to take obvious move actions. All of these give the feeling of "traps" without actually assigning them space on the grid. Of course, if your PCs fail to heed these warnings you will want to spring a trap and indicate where it hits.

Answer 7

You could use "Secret ink glasses" : you mark the traps on the map with invisible ink, then put the glasses on, and you're the only one that can see traps ! Pretty fun ;)

It's called polarizing ink, you can see an example here : Polarizing ink and glasse video example - Youtube

Answer 8

I would consider marking each square with something, both the trapped and untrapped.

You could also tie this visual to a feature, basically say "The blue dots denote the number of shallow pools of water, the dot is a pool, the blue is water. The dash means a tree root, the green means it is covered in ivy." Or whatever, but the idea is you could weave it into your narrative seamlessly and it could add to the experience.

Clearly something easy for you to remember, not too obvious, but by marking each of them you are creating uncertainty in the players and a sense of foreshadowing.

"What does two red dots means?" thinks one player aloud, while the another might say, "It is the green dashes that are dangerous." "Nope," says another, "Has to be the number three, three dots is trouble."

Answer 9

Assign coordinates to your map. Mark one side with letters and one side with numbers. Track, in your gm notes, which squares have traps.

For example: E8: Snare G6: Pitfall

Alternatively, use graphing paper as a smaller representation of the map in your notes, and mark the traps and other hidden things on there. Just cross reference as you play.

Answer 10

Track which squares are not trapped. Unexplored squares then could be either trapped or not trapped (Schrödinger's trap?) depending on who steps on them first. Shaping the battle map to more or less suggest the path, like this stalactite to that stalactite, would be much easier than trying to memorize a couple dozen nearly arbitrary coordinates.

Answer 11

The easiest way to do this with the least amount of prep time and game time is to use Roll20 and note the squares where traps are located using the drawing feature and the GM information overlay (which is invisible to the users). I frequently use this for things like trip wires, pit traps, falling stalactites, snares, etcetera.

Pros:

• You don't have to mark every square with some tedious arcane notation and remember what each symbol means. If it's confusing for your players, it will be confusing for you too. "What does the 3 mean this session? Hold on guys, let me check my notes..." Seriously, who has time for that either in prep time or game time?
• You don't have to worry about revealing a trap's presence until you're ready to do so (they successfully interrogate one of the Kobolds to reveal the places which are trapped) or a player triggers one. If a player triggers a trap, you can just right-click on the drawing you made to remind yourself about the trap and move it from the GM info layer to map layer so that the players can see it. No extra work necessary.

Cons:

• Everyone needs to have a laptop, netbook, or tablet to access Roll20.

If for whatever reason you can't or won't use Roll20, then I suggest Jason_c_o's excellent answer. Chess players mastered the art of referring to specific squares on a gridded game board long ago. There is absolutely no reason to reinvent the wheel, especially with a strategy as time-consuming and tedious as "mark every single square."

Answer 12

While Erik has an excellent idea I think it should be taken farther:

Once someone gets the idea that the floor markings are the guide it's simple enough to only step on squares with a symbol a kobold stepped on, or on squares which it's apparent a kobold must step on because they have no choice at that point. (A kobold retreats into the room, the symbol on the square by the door is certainly safe.)

Instead, lets mark every square differently. I'm no artist, I can't do a reasonable job of drawing thus but I can make a simplified version:

+- -----+
|tojklmn|
|vapioaq
|wyqbivt|
+----- -+

The gaps in the walls are the three doors to this room. As you know the kobolds went this way you know that "o" is safe--but what else is?

The kobolds know that any square with a letter containing a loop is safe, others are dangerous. Note that the door in the bottom is for luring intruders into danger, a kobold stands in the doorway and runs away when someone enters the room--they only see him running out through that door. While the driving rule will be simple the key is that it's only part of the design.