Agency Preserving Illusions

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What makes a hazard in a tabletop RPG fair? I believe that clues are what make hazards fair. They can be subtle clues, or even indirect clues, but if there are no clues you are playing a game of chance rather than a game of skill. Especially if hazards can kill a character dead with only a saving throw as potential saving grace, clues are critical (the issue is slightly blunted, though not removed, of the lethality rules are more forgiving).

This is relatively straightforward with physical traps, such as darts, daggers, and collapsing ceilings. Just think about the mechanism required for such traps and add description. Scorch marks, dead NPCs, holes in the masonry, dust on the floor in a particular pattern, watermarks on the walls, etc.

But what about illusions? Theoretically, an illusionary floor could cover a pit full of spikes covered in save or die poison. Sure, you would still get a saving throw, but having to roll a saving throw should come after making a mistake. So what is the clue for an illusion?

There has been some discussion of illusions by Courtney over at Hack & Slash. For example, this example of detecting illusionary pit traps suggests using magic saving throws after physical interaction is attempted (such as throwing a coin into an illusionary pit). And in a post about another illusion-powered trap, Courtney writes:

There should be at least a single word in the description of the object to indicate it’s chimerical nature.

For example, describing a rolling boulder as preternaturally silent. This approach is not entirely satisfactory to me, especially the saving throw method, because there are no clues at all prior to interaction. Moving to the second example, this is better (a clue is presented at the outset), but it also seems somehow artificial, and perhaps difficult to apply to non-visual illusions. I don’t think the “one word” rule is bad, exactly, but I think clarifying exactly what kind of clues illusions might create would be useful, especially when moving beyond examples of visual illusions that don’t make noise.

Consider this quite from The Deed of Paksenarrion by Elizabeth Moon (book 2, Divided Allegiances, chapter 13):

Young sir, if you think it is easy to produce even illusory fire, I suggest you try. My old master, who is well-known in the arts, always said that a fine, convincing illusion was far more difficult—because reality carries its own conviction, and saves its own appearances. If you make a flame, it is a real flame, and you don’t have to worry, once you’ve got it. But an illusory flame can go wrong in many subtle ways—even such a thing as forgetting which way the wind is blowing, so that it flickers the wrong direction.

Perhaps this is a potential answer. No illusion is perfect enough to not have any logical inconsistencies. So here is a simple rule of thumb similar to Courtney’s “one word” dictum. Every illusion has at least one inconsistency or “deja vu” moment (like the cat from The Matrix). Maybe something plays in a loop or doesn’t quite react correctly to the environment. I believe this could easily handle illusions involving any of the senses, because the heuristic is something incongruent, rather than something chimerical.

Potential inconsistencies may also, of course, be caused by something else that is not yet understood. For example, a flame flickering the wrong direction might also be an indicator of a draft coming from a secret door. So inconsistencies should not necessarily be seen as a dead giveaway of an illusion, but they are something that needs to be understood before a party can proceed without potentially subjecting themselves to the mercy of the saving throw dice.

8 thoughts on “Agency Preserving Illusions

  1. Chris McDowall

    Perhaps illusions are never fully opaque and don’t quite fit their surroundings. The fake floor hiding a pit is immediately visible as looking different unless in the dark or running. The fake dragon floats slightly and is ghostly in appearance.

    This ghost dragon can be scary in its own right, but it will never quite appear fully convincing as a real dragon.

    1. Brendan


      That would be an interesting variation, but I think it conflicts with the intent of the original iconic illusion spell, phantasmal forces. In the original writing, this spell was intended to make troop strength seem larger than it actually was in order to intimidate an opposing force. It was, in effect, a form of war game poker bluff. For that kind of effect, the illusion needs to be relatively realistic.

      Perhaps individual illusion spells should be more tightly specified. For example, phantasmal forces would not be a general illusion, but really just an illusion optimized for making it look like there are more soldiers. Further, it would not be usable to create soldiers where there were none, but only to cause something that is actually there to be more so or less so.

      Or riffing on both than and your suggestion, maybe if there are no soldiers to begin with, the illusion is more obvious and ghostly.

  2. Alec Semicognito

    I’ve found that if I don’t forewarn players that I’ll be dropping subtle hints in speech about unspecified dangers, or that sometimes I’ll be taking things they do in real life as things their characters do (like say a word out loud), the clues are wasted on them and they may get angry about them when the action is done.

    1. Brendan


      This is a good point. Part of the “clue infrastructure” should be instruction about what kind of things should potentially be paid attention to. For example, I include several different kinds of antitoxin in price lists, and also tell the players directly about the threat of poison. Magic-user characters could be told explicitly about telltale signs of illusions the first few times, or characters could encounter NPCs that warn about the dangers of illusions.

  3. Gus L

    I profoundly hate illusion traps – they always seemed like a bit of that “Tower of the Archmage” kind of gotcha dungeon. Saying that I think they have a place – the way to warn for them isn’t immediate (though the fire burning the wrong way is a great idea) it’s in the lead up.

    When you are going into the “Lair of Eyeballgnawer the savage Ghoultroll” an illusionary floor is stupid – yet if a party can’t figure out that there might be illusions in “The Tomb of Fellmage the unseen” that’s on their head. All traps shoudl be telegraphed a bit, and illusions are no different, but I think it’s fair to say that the level of magical skill involved means that they are limited to certain situations and that itself provides some warning.

    I also think maybe illusionary and magical traps would have a “bugspray” type item to deal with them, some kind of expensive dust of charm that is fairly mundane, but has limited uses and disrupts illusion if tested on them.

    1. The Recursion King

      I’ve had much success in the past with illusory chasms, where the danger is the illusion. No one has ever complained about these and much fun was had with players convincing their henchment to walk across!

      I’d be willing to give an illusionary floor over a pit trap a go. Likely, the floor would be a whole room floor which does not react to the lantern light as would be expected; the floor is not getting dimmer with distance as the walls are. That would tip the players off that something is wrong. Of course, their front line of four men at arms might have already tumbled down it if the players just open the door and march in…

  4. Picador

    I agree with Chris et al above: magical illusions should be telegraphed much the same way as non-magical illusions (e.g. collapsing floors, secret doors, etc). The “illusory floor over the pit trap” is a good example: the visual illusions might not match the rest of the floor due to changes over time, e.g. discoloration of the surrounding floor by stains or dust, or rubble strewn over the floor except for the illusory patch (where it would have fallen through). Similarly, an illusory wall might be betrayed by smells, sounds, or a draft coming through it, or by a blood spatter on the adjoining wall that abruptly ends at the illusory portion.


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