Monday, March 29, 2021

So You Want to Build a Dungeon?

You want to write a dungeon adventure for a classic style roleplaying game, and you want it to be good. How does that work?

What exactly does a “dungeon” imply and what is it as a game tool?

A dungeon is a specific kind of adventure, one that has its own form and which requires certain elements to be successful. More, a dungeon is a “location based adventure”—an adventure that will involve the exploration of a fictional space room by room. It’s certainly not the only kind of roleplaying adventure, but it’s the primary kind for a particular exploration, navigation and problem solving style of play that is both the oldest and still a compelling one. A dungeon must be a fantastical location, but it need not be an underground maze or cave system: buildings, shipwrecks, space stations, castles, formal gardens or the corpses of an enormous beast all make fine dungeons.

What is necessary for a dungeon adventure is to create a bounded fantastical space, “Rooms”, linked together in some order that the players can freely navigate: backtracking, turning, and determining routes. Within these Rooms the designer places obstacles and rewards. Traditionally this means a series set of stone corridors and chambers filled with monsters, treasures and traps. However, neither the aesthetic of the space or the nature of the inhabitants, valuables and challenges within are fixed elements of design, and reinterpreting the dungeon space can make for a novel and exciting adventure.

Likely when you decided to write an adventure you already had a story in mind, and that’s good, but since location based adventure is about the players’ decisions, that story will recede into the background. Given freedom to scheme and explore, players are as inventive and truculent as a proverbial herd of cats, and trying to force or trick them into telling a specific story is about as successful as ring-mastering a cat circus. Rather than a story, consider your ideas a “Theme”, one that will inform the “Ecology” and a “Layout” or map that together define the dungeon adventure. Putting a plot to it is likely to fail when the players, unaware of the plot, follow their own interests. This is the joy and burden of location based classic dungeon crawling, that its story has to evolve from player decision.

The most dangerous part of a designer’s story is a climax or ending because it’s very hard to include one without making dangerous compromises to the dungeon adventure form. Narrative beats make assumptions about how the characters within a story will act, and become very difficult to maintain when those characters’ decisions are being made by someone other than the author. Players decision making is unlikely to bind itself to even as simple a narrative structure: incident, rising action, climax, falling action and resolution. The players may decide that they wish to avoid the climax’s confrontation by siding with the antagonist or they may simply turn away from the rising action as they become distracted or the risk seems too high and the rewards uninteresting. Instead the dungeon designer is best building only the space for a story to unfold, and relying on the players to determine the narrative within that story.

NOTE: There is now a more in depth sequel to this post primarily about Dungeon Keying.

The first question of dungeon design is space. Before a designer can address the themes and story of a fantastic location they should consider the game mechanics of the location itself, to think of it as a board or arena for play. Space takes time to traverse, and in a classic roleplaying game time embodies risk: random encounters, torches running down, exhaustion and increased distance from the safety of the entrance. Thus a dungeon requires a Layout, some way of structure the Rooms of the dungeon that gives players choices about how they will navigate them, but is of a scope and complexity when those choices are meaningful. Traditionally, and still most effectively, Layout is organized and shown with a map. Drawing a map is easy enough, but still raises the question of what kind of map?

Thinking about maps is thinking about space and time, and not just fictional time. Consider the time you and your players have to devote to the game. A party role playing game explorers using a reasonably light rule set moves through roughly three to five rooms per hour of play, assuming 1-2 encounters or other obstacles in those rooms and a reasonable level of detail to poke at. For a one session, 2-4 hour game, a dungeon of 8 to 12 rooms should be sufficient. While multi-session games can utilize larger dungeons, these time constraints are still important because they help determine the limits of one session’s worth of exploration and so the placement of entrances and exits.

This basic scope is important because it gives the designer expectations and guidelines for size and complexity. Too much complexity or too many rooms and the players will never be able to make meaningful progress in the adventure or understand the layout. Too few rooms and too little complexity and the adventure risks not offering many choices, reducing play to a predictable set of scenes and encounters. After establishing the basic scope of the Layout there’s plenty of specifics to contemplate and RPG cartography has its own complex set of arguments, maxims and strong opinions; however, basic tips for designing usable dungeon maps include:


  • Avoid linear maps. Branches, loops, verticality, secret doors, rooms with multiple entrances and exits all make the map of your dungeon a puzzle that the players can solve. 
  • Consider the size and scope. Add empty Rooms to create space when needed and rather than a single sprawling location consider sub-levels or ‘nodes’ of 10-30 Rooms each.
  • Place multiple entrances and exits, especially if the dungeon is larger. Use locked gates, trapdoors, chutes, and secret doors to make discovering these exits and their relationship to the dungeon layout itself a reward.
  • Verticality is a traditional way to break up regions or “Levels”, but it’s harder to use within individual Rooms as it can be difficult for the GM to describe complex spaces: multi-level rooms and oddly shaped rooms are best used sparingly.
  • Symmetry is risky, while it can be a useful tool for hinting at secret spaces and encouraging player comprehension of a map, it also can easily lead to dull and linear maps. Before relying on it, consider both the fictional reasons for the symmetry, how it will affect play, and that in real architecture most symmetry is only partial. 
  • Most importantly, the map of your dungeon should have an internal logic: the placement of Rooms should make sense both fictionally and spatially. A throne room should be large and accessible through an opulent antechamber and guard room, not a kitchen or waste dump.

Not really. Any location has a story, a history that informs the situation the players find when they explore, there’s just no story for how the adventure within the location will unfold. Some events or endings are more likely than others, but the Game Master, and especially the designer, can’t depend on those likely conclusions to the adventure because it’s the players’ adventure, and players are unpredictable. Instead the Designer can set the situation, define the goals and personalities of the other actors (NPCs or monsters within the adventure—a distinction isn’t helpful here) and describe the backdrop.

Situations and History
Building a compelling initial situation is as much a part of adventure writing as designing a good map, but without underpinning knowledge, without some poised narrative energy—pent up and ready to be released by player interaction it will be hard to visualize and incorporate that situation. A good location based adventure may start in equipoise, with a situation more or less static, but ready to tip into disaster and action with player interference. Developing situations are also possible, but much trickier as they need to be built into the campaign as a whole, typically with a countdown, clock or index mechanic—something far beyond the scope of a single location’s design.

The history of the location and the stories of its denizens will set your initial situation, define the spatial layout and influence the outcome of the adventure. However, this information is not especially useful to either players or game master on its own. How the past impacts the present that the characters find themselves exploring matters but the intricate details of a location's history are largely unnecessary to run an adventure. Backstory is somewhat inevitable when building the location in your mind, but it’s not something that needs to be passed on to the reader. Backstory often detracts from usability, both by taking up space better spent on more accessible details, complicating the layout and by adding information that may make it harder for a Game Master to incorporate the adventure into their game. However, minimalism and the elimination of all history or backstory is as much a poor design decision as too much.

Backstory helps the designer build the location defining what spaces are, how they are used in the present and why they were built. It informs the attitude, relationships and nature of the location’s inhabitants (the “Ecology”) and can give the players clues about puzzles and obstacles within the location. Most importantly it defines the description and aesthetics of the location, its theme. Theme evolves naturally from the designers efforts to conceptualize a location, its history and the present situation, and fill out its details, but you shouldn’t waste it on an introduction that the players won’t read and the game master is likely to skim and forget during play.

Instead backstory, history and aesthetic Theme offer something that the designer can build into description and use to define their adventure as different from others. Maps, monster statistics and other mechanical aspects of location design won’t vary too much between similar adventures, but the Theme can. Saturating a location with a consistent aesthetics, and repeated Theme improves an adventure by making it easier to visualize, sticking in the mind and filling out details.

For the game master Theme makes expanding the necessarily limited descriptions of the Rooms easier by fixing an overall aesthetic, past and present situation in the mind that the game master can borrow from to answer unexpected questions. For the players a Theme offers consistency, allowing better visualization of the space and so greater ability to investigate or think up unexpected solutions. A game master operating with a well defined Theme will find it easy to describe details and expand on descriptions, giving the players more knowledge and tools to act inside the fiction. Players will also develop expectations and knowledge about a Theme, making them better able to decode what’s out of place and recognize clues.


  • Rumors and hooks almost always incorporate history and backstory, they represent clues to the location of treasures, the nature of obstacles or the goals of the opposition within a location. 
  • Build evidence and background stories into the location descriptions rather than relaying it to the Game Master, they’re useful only in as far as the players can discover them.  
  • History defines the appearance of a location: layout, building material, state of repair, existence or type of secret doors and traps—moreover it gives the players clues to them. 
  • Murals, carvings, graffiti and detritus are all defined by history and backstory, and they encourage player investigation while creating a sense of a living space. 
  • History and background stories help make the goals and attitudes of a location’s inhabitants more plausible and transparent.

With Layout and Theme, all that’s left is a greater focus on the inhabitants of your dungeon and the ways they will interact with the party, each other and the space itself. This dungeon Ecology is, as mentioned in the 1979 Dungeon Masters Guide, a fantastical one which needs to be comprehensible, not scientifically functional. Food chains and creature territories are useful, but the point is not to simulate a fictional world with rigorous fidelity—instead the goal is to create a web of plausible and recognizable connections between the creatures and the space of your dungeon that players can observe, understand and exploit. The most obvious and useful of these are the relationships among the inhabitants of the location, its “Factions”.

Beyond continuing the aesthetic coherence brought by a good theme, Ecology includes the relationships of predator and prey or tyrant and underclass among the inhabitants. For these stories and relationships to matter they must be something the players can see and exploit. Within factional relationships there’s room, and even a need for story, but again, the details of the past are less important than a present that the adventurers can interact with. Details such as the reasons for factional animosity are useful at times especially as they offer information that players can capitalize on when they inevitably become enmeshed in faction politics and struggle, but most important are the power relations and attitudes between the location factions, the nature of their leaders and what they will demand to work with the adventurers.

While it’s common to think of factions as others groups of intelligent and organized creatures within a location this need not be the case. A faction can be an individual creature, either a powerful predator, or even a weaker creature whose very lack of power makes them an almost natural asset for the adventurers. Likewise factions need not be intelligent, packs of animals or a single dangerous beast can define the relationships between the inhabitants of a location, and their goals and reactions to adventurers are useful to consider. Nor do factions have to be native to the location. Rival adventuring parties or other intruders may also contest the players goals within a location and offer enemies, allies or simply complications. To design the Ecology of a location one should consider any inhabitant or likely intruder whose existence and plans can disrupt the location’s present situation and offer advice on how they may interact with the players’ characters, even if it’s straightforward.


A difficulty in creating a useful dungeon Ecology that still follows a specific Theme can be the nature of the inhabitants. While there are hundreds of monster manuals and bestiaries it’s sometimes hard to find a pre-written creature that: fits the appropriate level of the adventurers, feels at home in the particular space and has the abilities and goals to match the factional structure and aesthetic. While inventing new creatures is one of the great joys of adventure design, the process itself can be daunting, especially in a more complex system, instead it’s often easier to use the stats from an existing well known creature and simply describe it differently. A goblin can have the same statistics as an angry villager or a puckish, unheimlich fey. When this reskinning doesn’t feel quite right, slight adjustments or swapping special abilities can usually fill in any discrepancies. A pig beast might be stated as a mountain lion with more HP (the cat’s leap becoming a boar charge) or as a bear without claw attacks and its hug mechanic replaced with a charge mechanic.

Reskinning isn’t just for creatures though, it can be applied to other obstacles and traps as well as to treasures, spell like effects and magical items. Generally anything mechanical can be described to better fit the Theme and Ecology of your adventure. Not only will this make stating your adventure easier, but it helps encourage greater player involvement and interaction because the threats characters face aren’t as easily defined with system knowledge, but rely on player observation to evaluate.


  • Consider the locations of faction food and water source and waste disposal, not only because these create coherence, but they also define faction territories and offer ways to threaten or destroy the faction. 
  • Not everything needs to make ecological sense in a literal way of having food sources and a lair, but everything should have a place within the larger ‘ecology’ of the location, meaning relationships with other inhabitants.
  • Define the leadership, goals and concerns of each faction, even if they are simply to find prey. Knowing the fears and price of a creature makes it much easier to determine how characters can enrage, befriend, trick or distract it. 
  • A faction leader or other NPC doesn’t need a lot of detail to come alive, a memorable physical characteristic, a few adjectives, and a sentence describing their “price” and “fears” is usually enough. 
  • For larger more important factions create an “order of battle” that lists its numbers, resources and a few tactics it will use in response to likely threats or strategies. 
  • Don’t feel bound by existing monster/spell/item descriptions because the internal coherence of your adventure is more valuable than fidelity to a manual. Existing statistics provide guidelines and models, but even in complex systems they can be reskinned and used differently quite easily.  
  • Random encounters and random encounter tables are a key to dungeon design, not only do they create time pressure, but they also introduce your factions and offer opportunities to encounter their representatives outside their lair.

The ultimate goal of Ecology, Theme and Layout is Coherence. For both the Game Master reading it and the Players who experience it the adventure needs to feel connected, to make sense as a whole. Creating a coherent adventure is a test of how well the aspects of Layout, Theme and Ecology blend at their edges and support each other, because despite the way this advice is structured, they overlap and mix rather naturally.
Coherence is especially important because the space is fictional and fantastical, meaning that visualizing it and understanding it require more imagination than visualizing a fictional real world space. Design and description need to work together to build some sense of plausible order, one with fantastical elements that depart from the real, but which still contains internal logic. Coherence is hard to quantify, as it accretes from other elements of design, but the goal is to create an adventure that’s identifiable as a “dragon’s cave” rather than “a cave with a dragon in it.”

For the GM coherence and consistency allows for greater ease in adding detail, and provides an understandable whole, a narrative of the location itself that’s easier to remember then disparate elements. For the Players coherence allows greater interactivity with the setting because there’s an internal order to the location that they can unpuzzle.

Finally, the necessary preparations are complete, the mise en place of the adventure is ready—a map is drawn, factions prepared, rumors written, theme and initial situation readied. As a designer, you’re ready to put in the meat of the adventure—the keys that describe its fictional space and that GM will rely on to run it. There’s a lot of art to keying, it’s a strange combination of technical and poetic writing. A good dungeon key must both clearly and efficiently convey descriptive information and inspire with evocative or poetic language. It doesn’t just need to be clear to the reader, but must also offer sufficiently succinct and inspiring language for that reader to convey the description to Players, who in turn will interrogate the description.
  • Beware of formalism. While a repeated structure for each Key can help Game Masters run an adventure, one that contains too many elements or underused elements is distracting. A Key is still evocative, creative writing—not a mathematical equation. 
  • Don’t use 'read aloud' boxed text, it distracts from room contents and disrupts the flow of the Game Master’s natural speech. 
  • Start your description with the most important things in the space: dangers to the PCs, followed by the most obvious aspects of the Room.  
  • Be as concise as you can, digressions and extraneous detail can make descriptions unusable. You only have a few sentences for each idea before it becomes confusing, and only a few of these paragraphs per room before the early ones are forgotten. 
  • Despite a shared need for concision, Room keying is not technical writing, akin to a computer code, architectural specifications or a mathematical formula. You won’t be able to include every detail, so the details you can include should be evocative and inspire the Game Master to fill in what’s missing.  
  • Describe what’s in the Room, not what it used to be. Visible remnants of the past can be part of the description, but should be minimized unless it is relevant to the present obstacles in the location. 
  • Describe a space, not the characters exploring it. Unless some powerful unnatural compulsion is at work, the players will decide how their characters feel about what they are seeing, so avoid ascribing emotions and especially actions to characters. Don’t start with “As you enter the door”. 
  • Describe a space, not a scene. While inhabitants should be engaging in activities, this is part of the description of creatures, not the location. A location shouldn’t be static, so the designer can’t know the circumstances when the characters arrive in the room. 
  • Include senses other than sight when providing descriptions: lighting conditions, temperature, sounds, and odors are powerful description, and useful easily understood clues. 
  • Make you Rooms interactive, the more players interact with the adventure the more they will be thinking about and visualizing it. Even “Dungeon Dressing” that is neither treasure or an obstacle provides thematic context, makes future concealed treasure or threat more effective, and encourages players to spend time exploring. 
  • Beware of minimalism, brevity is key, but the Room key is the designer’s best chance to share their imagined space with the Game Master who will translate it to the Players. Offering poetic, concrete details and specific words that leave a strong impression is the best way to do this. 
  • Use a consistent tone and style of language. “High Gygaxian” bombast or humorous familiarity can both work, but switching between them frequently also switches the tone of the adventure and confuses the reader.
For a more in depth look at room keying this post on the keys in the dungeon section of 2019's Descent to Avernus may be useful.


  1. Good stuff, usual.
    : )

  2. I would like to see an extended example of Theme, maybe from some old chestnut of a module everyone knows.

    1. Perhaps some day, though I would say that Broken Bastion is for example "Crashed Space Elf Weapon Platform" themed. For old adventures it seems that the theme is usually "D&D Dungeon", which may have worked in 1980, but feels pretty tired these days. Outside of that Thracia is pretty good, using the elements of D&D dungeon in somewhat novel ways with a more classical era ruined city theme. Isle of Dread manages a jungle island adventure thing and Ravenloft (despite many flaws) hits a good midnight monster movie vampire kitsch theme.

  3. Hey! I thought you left forever. Nice to see you back.

  4. Hey Gus, as I browse over your articles this one really shines! I just wanted to give you that positive feedback.


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