The Invisible Dungeon

Previous editions of Dungeons & Dragons were characterized by vast dungeons full of ridiculously lethal traps, equally lethal monsters and often a complete lack of common sense when it came to monster placement and dungeon design. Nowadays in third edition we DMs no longer need to set our adventures in catacombs and underground lairs, and players are just as likely to find themselves exploring cities and wilderness. However, you may be surprised to learn that even when you’re braving the arctic or riding over a city on a hippogriff’s back, odds are you’re still in a dungeon. When is a dungeon, not a dungeon? When it’s an invisible dungeon. Read on and I’ll explain.

Note to players: This article is categorized as DMs Only. Do not read this article unless you are a DM, otherwise you it may spoil the fun for you if your DM chooses to use it.

Roleplaying games have certainly changed and developed over the years. Originally, the entire game was dungeon crawling, given D&D’s origins in miniature wargaming, and ideas like plot and character development were ignored. The game was very much still a mediaeval wargame on a smaller scale, except set underground with wizards. I won’t pretend to have experienced the game much prior to third edition, but adventures nowadays have really expanded outside the dungeon crawling monster-whomping treasure hunt, to the point where some groups play entire games without making a single attack roll or even rolling the dice much at all. Entire roleplaying systems have been created where the game master is referred to as the Storyteller, reflecting those games’ emphasis on telling a story about unique individuals rather than killing underground critters and taking their magic swords.

Those games, however, are not D&D. I’ve been researching adventures lately in order to find out what it is that holds together an adventure where you don’t have a dungeon to do that - well, when I say researching, that’s a fancy way of saying I’ve been reading over my back issues of Dungeon. If we take a look at the latest issue I’ve got, none of the adventures are set in a dungeon but they still tend to fall into a similar pattern. The Beasts of Aulbesmil, for example, might be set in a remote village instead of underground caves, but it still opens with an adventure hook as the “excuse” to get the players in, and it’s still defined in terms of places, ways between those places and creatures that will be encountered. The difference with today’s D&D adventure is not that it isn’t always set in a dungeon, but that it isn’t always set in a literal dungeon.

The Invisible Dungeon

As a DM, I’m sure you’re already familiar with the layout of a standard dungeon. A literal dungeon (and, I’m told, the original D&D dungeon) is a network of corridors and chambers built underneath a castle, an idea expandable to cover catacombs, sewer systems, ancient underground ruins, tunnels constructed by animals or monsters, and even natural caves. It works well in a game due to its self-contained, isolated nature, as I’m sure you’ve read in the Dungeon Master’s Guide's “Behind the Curtain: Why Dungeons?” sidebar.

Of course, expanding the definition of “dungeon” has no reason to stop at being underground, or even in an enclosed, isolated space - at least, not if you’re taking those terms literally. As The Big List of RPG Plots says, an old idea can be taken metaphorically instead of literally. A DM writing an adventure need simply work out what it is that makes a dungeon a dungeon, what it is that makes it such a useful tool for the DM. As the aforementioned sidebar defines:

A dungeon is really nothing but an adventure flowchart. The rooms are encounters, and the corridors are connections between the encounters, showing which should follow which. You could design a dungeon-like flowchart for an adventure that didn’t take place in a dungeon and accomplish the same thing. One encounter leads to two more, which in turn lead to others, some of which double back on previous encounters. The dungeon becomes a model, in this way, for all adventures.

The concept of a dungeon, therefore, does not need to be limited to something which physically resembles a set of catacombs, at least not in D&D. Of course, a DM will never speak to his players of anything but a network of enclosed chambers as the “dungeon”, but when he is writing or planning his adventure, he can make use of this metaphor and the advantages that go with it. Therefore, the dungeon is still a core concept to Dungeons & Dragons, even in this post-dungeon era of the game. This new-style “invisible dungeon” often slips under the radar of players who praise D&D over other games like Vampire and Exalted - the latter are storytelling, while D&D is still very much dungeoneering with an optional storytelling aspect.

Dungeon Concepts as Metaphor

When running more free-form, non-dungeon adventures, I sometimes find my players confused as to the direction of a game I’m running - I don’t make any pretences at being the world’s best DM! One mistake I have continually made is to ignore the “invisible dungeon”. In order to reap the benefits of a dungeon, it is important to retain the basic concepts of a dungeon, at least in a metaphorical sense.

The Dungeon Itself

A dungeon in D&D is very much defined as a location where adventures occur. An adventure can be anything as long as it’s going to interest the players and allow them to make use of their abilities. As this is D&D, there are some generally immutable things that any player or DM should draw out. We can expect that the player characters will overcome challenges that use up their resources (or else they’d get no XP), and we can expect there to be a few altercations (or else the combat characters will have nothing to do). We can expect there to be some events requiring the use of non-combat skills (primarily for the rogue) to give characters a chance to be proud of the opportunities their abilities have unlocked, excuse the pun.

Still, the point about a dungeon is that it’s isolated and strongly defined from the players’ perspective. In a real dungeon the players can see where they can go and where they can’t. They can tell what things they have to fight, what things they should avoid, and so on. They know that they can do anything within the limit of their power, and are very rarely confused as to what direction they can go in order to keep the game going forward - that last one is vital to keep the game fun. An invisible dungeon is no different. Do not simply lose your characters on a town unless the adventure considers the adventure area a kind of dungeon.

A dungeon might be defined as an adventure site separated from everything else. This doesn’t mean that a figurative dungeon has to be in an out-of-the-way place, although that’s often a good choice because it lets the players visit interesting locales and stops them from wondering how all the adventures manage to happen in the same country. It does mean that the adventure has to be self-contained and limited in scope, since otherwise the players will get completely lost in the vastness of it all. And of course, while a physical dungeon usually occupies only a small area, an adventure might cover an entire world (or even many worlds!).

The Entrance

All dungeons have an entrance. They mark the beginning of an adventure and let them know that from here on in they’re pretty much on their own. The town guard will not enter into the adventure with them, nor will the helpful high-level wizard NPC they met two adventures ago. They cannot simply leave mid-adventure. They might meet someone friendly along the way, but they’re a lot more likely to find something dangerous. When they accept their task and walk through the entrance, they know all this, and do it anyway, because it’s what adventurers do.

Obviously, it requires more thought and creativity to decide what your “entrance” will be when it might be a person, place or event instead of just a big door, but it must of course include the basic aspects of a big door. It must be easily encountered by the PCs without resistance, and must not be hidden from them otherwise they might miss it. It must be difficult for the average person to access, or else someone probably would have found it already; if everyone in the village knows about it, it must be too foreboding or dangerous-seeming for anyone else to have approached. The essence of the entrance is that the adventure cannot begin without it, that the PCs must easily find it and open it given their current ability, and that it must not fail to throw the PCs right into the path of the adventure. It might be led to by a plot hook, or be considered a plot hook in itself. A good example is an exciting encounter (always good to start a game session with one) after or during which the PCs learn something that hooks them into the adventure.

Anything which can happen to the entrance of a dungeon can also happen to this metaphorical entrance. Many players are familiar with the cave-in that blocks the party from leaving the same way that they entered, forcing them to find another way out in addition to completing their mission (or indeed, as the adventure itself). This might be represented by an NPC who hires the party (the entrance) to retrieve an item, which they do quite easily only to read in the newspaper that the NPC was assassinated by hobgoblins looking for the item, trapping the PCs in a perilous situation and forcing them to find another conclusion to the adventure.


Rooms are important divisions in any dungeon, each room hiding an encounter or a secret and preventing the PCs from being overwhelmed by the big picture. Luckily for them, it also prevents allied enemies from all noticing the party at once and descending on them in larger numbers than they can handle. The abstract concept of a room is a place separated from other the other places in the dungeon. Kind of a microcosm of a dungeon, which is an adventure site separated from everything else, a room is an encounter site separated from other encounter sites.

Each room has something different about it that the players can remember, which is especially useful if they have to go back to a place for any reason. The players might talk about returning to “the room where we fought the gnolls”, or “the big room with the statues”; similarly they may speak of returning to “the bridge where we fought the gnolls” or “the temple of Nalost in Lindale”. “Rooms”, or encounter sites, need not be physically right next to each other any more, and may be spread out over large distances, but the PCs must always know how to get from one to the other without much bother.

A great advantage of this format over a real dungeon is that you have much more flexibility in creating encounters when you’re not limited to cramped, underground rooms. Outdoors flight-based combat over huge areas is possible, ranged weapons and taking cover can come into play even more, and natural terrain can be put to good use. Encounters can take place outdoors, in public buildings, in the middle of a market, aboard ships, across rooftops, in the sky on flying mounts above a city, across huge open areas, on the road, in the wilderness and on other planes. This can bring in a lot of new and interesting challenges.


The scale of a wide-area adventure adds an extra challenge for a DM designing an adventure. As I said earlier, if you threw the PCs into a city and told them to find an item, your players would be as lost as tourists, overwhelmed by the immensity of such a huge and undefined adventure site - remember that your players have no idea just how far-reaching your adventure might be until they finish. The “entrance” will hook them into the first “room”, but if you’re not careful you might lose the players there as they find themselves with no idea where to go next. The answer is to connect “rooms” with obvious “doors”.

The abstract concept of a door is something which connects two rooms together. Remember that by our previous definition of “room” as any kind of encounter site, so the DM has to be able to link together sites using methods appropriate to the individual rooms. Suppose for example that the players are ambushed on both sides by gnolls as they cross a long bridge - this is the “room”, or encounter site. If the next encounter is with a friendly NPC such as a local lord in his mansion, perhaps the lord he rides up just after the fight, congratulating the party on their fine combat skills and inviting them to dinner.

A door must always be obvious once the encounter ends, or immediately if there is no encounter in this room - some rooms contain only minimal features and exist only to establish a tone and lead on to other rooms. (The exception to this is hidden doors, which I’ll discuss in a moment.) This only means that that non-hidden doors should always be easy to notice, not that they must always be easy to go through. Just as real doors may be stuck, locked or trapped, your travel to the next encounter site might require brute force, might require the application of skill, or might simply be dangerous. Given how varied your “door” might actually be, there is a great array of what constitutes “brute force”, what skills would be required, or what XP-earning dangers they might face.

You don’t only have to limit your encounter to having one “door”, which is just as well since you can’t always rely on players thinking to take a certain course of action. The PCs in the previous example might find a clue on the lead gnoll’s body, manage to take one back alive for interrogation, or following their tracks back to their lair. The simplest way to handle this is to have all “doors” lead to the same “room”, perhaps covering up one or all of the other trails once they discover their first one. For example, if they find the tracks but check the bodies before they leave to follow the tracks, they find no gnolls left alive and no clue on the leader’s body; if they interrogate the prisoner first they still don’t find a clue and the tracks have been covered by snow by the time they’re done. You might even draw plot twists from the clues they left behind - perhaps someone else found the tracks and followed the PCs to the gnoll lair. If the PCs fail to pick up on any of these “doors”, it helps to drop a hint - perhaps suggest to the players that they might want to loot the bodies.

A more complex, but perhaps more interesting alternative is to have multiple “doors” take entirely different paths. In this manner the players might not even need to visit certain rooms, and again, whatever rooms they miss out on might lead to encounters later. In our gnoll example, the PCs might find a dwarven waraxe on the lead gnoll’s body that has runes tracing it to a certain clan, and go to the dwarves with the axe either to accuse them of supplying weapons to gnolls or to return the axe hoping for a reward. Perhaps this “door” of getting into the dwarven stronghold has a “lock” in the form of being well hidden (requiring Knowledge (geography) to find), or is “trapped” in the form of dwarves who don’t much like outsiders encroaching on their ancestral lands. Of course, if the players ignored this and interrogated a gnoll, the gnoll might lead them to the person who hired them to kill the party - an entirely different direction. Generally, the adventure will always end up in the same place no matter what paths are taken. If you’ feeling really ambitious though, you could plan out entirely different endings depending on the players’ choices, although this requires more work. In general, it helps to keep the number of missed encounters to a minimum to prevent wasting time on rooms the players will never see.

However, there are some occasions where it’s a good idea to have “doors” that the players may never find and “rooms” that the players may never see. This is when you’re using a “secret door” - a kind of a door that the players generally do not see without some exceptional circumstances such as deliberately looking for it or the application of skills, magic or special abilities. These are always nice because they let players feel good that their skills and class abilities are useful. The idea behind the secret door is always to give the PCs a bonus or a shortcut. One example might be a seemingly unimpressive brooch carried by a slain villain, which an Appraise or Knowledge (history) check reveals to be a priceless historical relic. This kind of door doesn’t lead the players on a different path - indeed, some doors might be dead ends or red herrings that force the players to go back to a previous door they’d discovered but ignored. “Shortcut” secret doors might be well-hidden clues that lead the PCs straight to a certain encounter without facing the dangerous encounters ahead of it, such as evidence that proves a man innocent and saves the party from tracking down the real culprit on their own and convincing him to confess.

The final rule of doors is to never, ever leave the players with nothing but apparent dead ends. While an occasional well-placed stumper might be an enjoyable challenge, players will just get frustrated if they can’t work out what should be happening next, and frustration and boredom must always be avoided if the game is to be fun. It’s also not a good idea to routinely hint PCs toward the “doors” since this would be “leading them by the nose”, which destroys the players’ free choice. However, leading by the nose is preferable to boredom, so if you find that your players have missed all of your doors and are truly stuck, throw them a hint to keep the game flowing.


A corridor in a dungeon is essentially a variant of a room, the primary reason for which is to hold other rooms rather than an encounter. As such, it’s not usually an encounter area on its own, but it is somewhere or something that leads to numerous other encounter areas. It may be an NPC wizard who can easily provide divination spells (though perhaps at a price), an informer who can provide numerous sources of information, or a list of people suspected of a crime. A corridor is like a hub for numerous rooms, and could be anything that will lead to a number of encounter areas. Of course, corridors might be trapped, and as such the wizard’s divinations might be unreliable at times or the informer might report the party’s own dealings to anyone willing to pay the right price.


A wall is what keeps rooms - encounter areas - apart from each other. In a physical dungeon it’s usually stone, but when encounter areas are further apart the “walls” are whatever keeps the player characters from seeing and travelling to other encounter areas. Most of the time, this is just due to the inherent limitations of what your character can and can’t do and perceive. Just as you can’t walk through a wall without using a door, you can’t follow the gnolls to their hideout until you find their tracks, you can’t be invited to the local lord’s dinner until he approaches you after the fight with the gnolls, and you can’t find the villain’s hideout until you interrogate the gnoll for the location.

Just like real walls, of course, you can often overcome them at higher levels without bothering with doors - usually by going through using magic. Interrogating the gnoll isn’t necessary when you can just Scry on the villain. Travelling through dangerous terrain isn’t necessary when you can teleport Until you can pass through walls, though, they provide an excellent method of making sure the entire adventure doesn’t take place in one spot.

Monsters and Treasure

Monsters and treasure, in an abstract sense, are… actually, they’re still just monsters and treasure. In fact, sometimes a wall is literally a wall, a room is an actual room, a door is an actual big wooden door and a dungeon is an actual castle prison. Killing monsters and taking their stuff is totally inherent to the game, and it’s that concept that has hundreds of thousands of people paying monthly to play World of Warcraft. I’m sure there’s a way to metaphorically kill metaphorical monsters for XP and take metaphorical loot to sell in a metaphorical shop, but right now I’m entirely happy whomping kobolds/ogres/mind flayers over the head with swords/axes/magic and taking their gold/weapons/magic items.

Now if you’ll excuse me, I have some invisible dungeons to go write.

Comments (5)

Valegrim (March 19th, 2006)

Interesting article; I wrote some posts to your comments on Paiso. Only one thing to add; I have found that if you use archtype npc as prime movers then your pcs get less confused. I dont use flowcharts myself; but I suppose its possible; I never used flowcharts much in programming either; but rather used unicode which is a series of comments about what various coded sections do or should do; which probably amounts to the same thing. I would be interested in how you would flowchart what I wrote for your post; keep in mind it is only an outline.

somebody else (December 29th, 2006)

Actually monsters and treasure are challanges and rewards — the challanges do not have to come from NPCs (especially not “monsters”) they could come from nature etc.,

Treasure does not have to be gold and jewels it could be contacts, or allies etc.,

jonathan (October 15th, 2008)

Ok, I’ve read this twice now (once a long time ago, bookmarked in my google reader folder; and now I just got redirected here from Wax Bank’s site). And I must say… even after two reads - this is just an amazing piece or work. Another fine example of RPG blogging at its best.

I feel a bit sheepish asking - but would you consider submitting it to The 2008 Anthology of Roleplaying Game Blogs? I recently announced this new project over at The Core Mechanic if you would like some more information. Cheers — JJ

Alex (March 3rd, 2010)

I am not sure I quite understand this concept. I will probably re read it.

anndelise (November 30th, 2010)

I really like this analogy. I’m new to GMing and have been looking for resources to help me more easily create adventures etc without blocking me into a linear format. I think that a good combination of this article, 5x5 method, fronts, and maybe even “how to host a dungeon” with this analogy in mind…I think these will be great starters for me.

Thank you for such a cleanly written lucid article.

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