GM Advice: The Illusion of Dungeon Detail

In a large dungeon or megadungeon (such as Gloamhold) a GM can never be perfectly prepared. No one has the time — or I suspect the patience — to prepare hundreds of different encounter areas.

Dungeon Entrance by William McAusland (Outland Arts)
Dungeon Entrance by William McAusland (Outland Arts)


When the PCs are in danger of wandering out of the area the GM has fleshed out, disaster looms. At this point, an inexperienced, tired or stressed GM can panic and either the session comes to a juddering halt or the quality of GMing plummets dramatically. Neither situation is ideal.

I’ve found the following tactics handy in providing the illusion of detail without flogging myself to death preparing countless areas and encounters.

  • Random Encounters: The wise GM has a small pool of detailed random encounters to hand. Such encounters enable him to slow down a party’s progress, if they are heading in a direction he has not yet detailed. These encounters don’t have to be particularly deadly, they just have to slow the player down. Dungeon wanderers (gelatinous cubes, dark mantles and so on) or even other bands of adventurers make great add-in encounters. Chance encounters with other adventurers don’t even have to end in combat! Padding out a session with pre-designed random encounters gives a GM breathing space to prepare the section of dungeon ahead of the PCs.
  • Blockages: The actions of burrowing monsters, the side effects of powerful spells or even just earth tremors and earthquakes can temporarily block off access to part of a dungeon. If it’s rained recently, flooding can also create an area of all but impassable terrain for lower level characters. Once the GM has prepared the relevant dungeon sections, he can remove the blockage — the flood waters subside, the powerful spell effect wears off, the dungeon denizens clear the blockage themselves and so on.
  • Powerful Monsters: As effective as a blockage, placing a monster or pack of monsters the party know they can’t defeat in their path is a great way of diverting a rampaging band of adventurers. Use this tactic carefully. If the PCs don’t realise how powerful the monsters are, things can go horribly wrong.
  • Sub-Levels and Side Complexes: Dropping in a small side complex of rooms, or an access point to a self-contained sub-level can divert the party long enough to give the GM time to prepare the upcoming area. These small “mini-dungeons” don’t need to be fully fleshed out. The GM just has to have enough details to wing it. The players will likely never know as long as the monsters and treasure make sense in relation to the rest of the module.
  • Cry for Help: In a similar vein to Random Encounters, the party might encounter someone who desperately need their help. Perhaps, they encounter an escaped prisoner or slave who needs to be escorted to the surface. Alliteratively, they could come across a lone adventurer searching for his companions who just happened to go missing in the part of the dungeon the GM has prepared. If you use this strategy, be sure to reward the PCs for their aid. The NPC might even become a regular fixture in the campaign!
  • Dungeon Dressing: I love dungeon dressing. I love it so much Raging Swan Press released a 300+ page book (GM’s Miscellany: Dungeon Dressing) devoted to the subject. In the context of the illusion of detail, dungeon dressing fulfil two important roles: it both slows down the PCs (as they investigate the mutilated body, strange graffiti daubed in blood or whatever) and helps the GM to add depth and verisimilitude to the dungeon.

When using these tactics, don’t use only one or two. A clever GM mixes things up a bit so the PCs don’t realise what he is doing. Using a mix of the above tactics helps the GM maintain the players’ suspension of disbelief and keeps the session running smoothly.

Help Fellow GMs

Have you got any tricks or tips for adding the illusion of detail to your dungeons? If you have, share them in the comments below and help your fellow GMs build better dungeons today!

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Creighton is the publisher at Raging Swan Press and the designer of the award winning adventure Madness at Gardmore Abbey. He has designed many critically acclaimed modules such as Retribution and Shadowed Keep on the Borderlands and worked with Wizards of the Coast, Paizo, Expeditious Retreat Press, Rite Publishing and Kobold Press.

15 thoughts on “GM Advice: The Illusion of Dungeon Detail”

    1. You don’t just have to use hard encounters. Encounters with smaller monsters, like goblins or kobolds can be very challenging, even for high level players, if you use them right. A half dozen goblins behind a spiked barricade, throwing spears can be a pain, especially if the part notes that the ceiling in the area is not exactly the best, and area of effect spells risk collapsing the tunnel. Now, the players have to deal with the barricade, and the goblins with spears, either chucking or poking them through holes, if they try and climb the barricade. And area effect spells, such as fireball, and others are removed. Now, if the wizard does tend to keep sleep, or gas spells, you can use slightly more powerful critters, just to make them have to think of a way around it, but this can slow down a party even better than the big monster that they can’t beat…..

      My other issue with the big monster method, is that if the party discovers it, it likely will discover them…. and having it refuse to chase them, as you put it there just to keep them away, kind of loses the suspension of disbelief, and if it does chase them, they may find themselves in a world of hurt.

  1. I make up 3×5 notecards of “stuff” during odd moments. Brief encounters, traps, dungeon dressing, NPCs, room descriptions, what ever strike me. Then when I get stuck or caught off guard during the game I can pull a couple of cards and have something all set up and ready to go at my finer tips. Having pre-started monsters, traps etc is a huge time saver, and the NPC encounters help when my creativity is running low at the end of a long session.

  2. The first time I ran Undermountain in a 2nd-edition D&D campaign, the party had recently had a tough fight with a vampire (it ended with the vampire running away). When the party entered the dungeon, the very first room had a rat scurry out of sight just as the group spots it.

    This was actually from the by-the-book description, but the players assumed it was the errant vampire in rat form and immediately went chasing after it. Before they could catch up with it, they ran afoul of one of the other denizens.

    For the remainder of their foray in Undermountain, I used that rat to lead the party around. If the group was near an interesting landmark, or an unusual combat situation, I would have the rat scurry by, and the PCs would drop everything to go after it. By the time they had finally caught up to the rat and discovered it was mundane, they had already been through half of the first level.

  3. Sub levels are a great addition to any adventure. I had one known as the web for undermountain which had all the usual giant spiders, ettercaps and aranea, the final boss was a witch (the widow…) protected by a fifty foot wide spider, so large the party thought its legs descending from the darkness were actually rock columns.

    i also inserted this sublevel into another adventure for a different party as a boost to thier exp. Scribble away on squared paper when you have spare five minutes and see what leaps out of your imagination :).

  4. Regarding minor encounters:

    It can be easy to forget how much minor encounters deplete spells and other limited resources, including healing. If the players burn a one-use-per-day ability on those goblins throwing spears, it’s an ability they won’t have when they get to a major planned encounter. This means that either they have to be very selective (and creative) in how they handle these random encounters, or major encounters are harder than they otherwise would have been, so even a fairly low-level set piece encounter can be a major fight. This is a good thing. And, of course, if they withdraw and regroup (and heal, regain spells, etc.) after a few of those minor encounters, when they get back the big baddie will be prepared and waiting for them.

    Also, of course, I’m very much in favor of dungeon dressing. (also of Raging Swan’s books; I have them all, to the point of even printing out the ones I bought in PDF) Admittedly I’m a bit biased here — I didn’t become a random generation table geek because I wrote TableMaster; I wrote TableMaster because I’m a random generation table geek. But I’ve always been big on having random elements of description for everything. Aside from the useful stuff (and that rat!), dungeon dressing (or urban, wilderness, etc.) serves another important function: disguise. It’s much like rumors: If there’s only one rumor available at the tavern it’s obviously important, but if the players are presented with a dozen, they need to sort through them to figure out what’s signal and what’s noise. Likewise, if you have some bits and pieces of description for *every* room, the significant things won’t be blatantly obvious and it will feel more realistic.

    1. Absolutely. Having cool little details sprinkled throughout the dungeon is a huge part of building a “proper” dungeon and for elevating your players’ play. Only having described things in major/important encounter areas is a huge flashing sign to your players. There’s nothing wrong with getting them to engage their brains!

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