Crafting an Infinite Dungeon for D&D


Not that long ago I ran across, or rather, ran across again, Sly Flourish’s overview of Frank Mentzer’s Dungeon, a sort of replayable or infinite dungeon for D&D. It was something I shrugged off as novel but inconsequential when I first saw it. Likely because it was focused on Basic D&D, BECMI D&D, which was not something I was interested in playing or running at the time. However, now that I’ve had years of running more games and put a lot of effort into making a useful DM’s Binder, I better understand the usefulness of backpacker resources, the sort of things included in my DM Binder’s “Parachute File.”

Whether it’s the party going off the rails in a different direction from your session prep, needing to throw something together because it’s a pick-up game, or you ran out of time to prep, having go-to resources for a fun night of D&D (and other TTRPGs) is nice. And that’s what Mentzer’s Dungeon does, according to the original post by Mentzer he’s run it dozens of times, even for the same players, and they have never noticed it’s the same dungeon.

According to Mentzer, he has it down to rote memory, including what the party is likely to find in each part of the dungeon:

Entry: Graffiti from previous visitors (containing clues if you search)
First Room: Debris in corners… including animating skeletal bits. (Possibly including cigarette butts and McDonald’s wrappers, if you like the humour element.)

Lower right corner: An ogre lair, possibly two (male & female, possibly preoccupied).
Lower left corner: Big alien in chair (original Alien film), but just a dead giant — whose corpse is full of bats and pests.
First rooms north (L/R): Things-are-not-what-they seem. Vampires quietly sleeping (just zombies), other tricky ideas, all low-challenge

Top left: Defenders with a double ballista aiming down the long hallway at the PCs invaders, placed to guard the side rooms (heavily protected vaults of loot, or pet dinosaurs, or…)

Top Center: The finale! Dozens of goblins, with hobgoblin guards, having a religious ceremony. You might break in thru secret doors behind the high priest; you might charge in from the entrances. Good news: Most are unarmed (church service). Iffy news: Armed guards and the High Priest (spells etc). Worst news: They worship a table with a boar’s head strapped onto it — and it can animate. (They call it TUSK, and I cue the drum-beat song by Fleetwood Mac…)

From Mentzer’s original posT

Now you may be thinking, who’s this Frank Mentzer guy and why should I care about his ideas? Good question.

Mentzer Basic D&D & The Red Box

Well, if you didn’t know, Mentzer was a designer/editor at TSR during the heady early times of Dungeons & Dragons. Most notable among his contributions to the game and hobby was the 1983 revision of the iconic basic set, known fondly to many nostalgic gamers as The Red Box. Yep, the classic one with Larry Elmore’s dragon busting out of the frame on the cover.

It was the introduction to D&D for an entire generation of fans and his revision did a better job than previous editions of explaining how to actually play the game. And in case you weren’t aware the Basic Rules in the set is the ‘B’ in BECMI D&D. Needless to say, I think that’s enough industry credit to make listening to his words worthwhile, even if you don’t 100% incorporate the knowledge for your Dungeon Master style.

About Mentzer’s Dungeon

Mentzer’s Basic D&D Dungeon is almost laughably simplistic. It’s nearly symmetrical in design with roughly two dozen distinct chambers and half as many secret doors. Here you can see an interpretation of Mentzer’s dungeon for Basic D&D from Dyson Logos. It may be simple but that’s what you want for an easy and on-the-fly resource for D&D.

Mentzer's Dungeon, Drafted with Owner's Permission by Dyson Logos

While looking it with more practiced eyes I wondered, could I make my own?

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Making an Infinite Dungeon for D&D

I spent some time reviewing the map thinking about what I did like about it, what I didn’t, and churning over the design choices and omissions. Such as, with such a simple and symmetrical layout why didn’t at least one of the group’s mappers realize it was identical to a dungeon they had been in before? Then I thought it best to write out my personal goals for such a project.

Infinite Dungeon Design Goals

  • A dungeon with high replayability
  • Address my perceived shortcomings of the original Mentzer Basic D&D Dungeon
    • Static layout
    • Bounded size
    • Established contents
  • Combine with the RRF Dungeon Creation Guide

Infinite Dungeon Design Considerations

Essentially, my goals show that I like the idea and I just want to make it a bit more versatile. Mentzer’s original dungeon only has two exits and much in the way of branching pathways. So, how would we be able to break from that locked in, static, one-page design for a dungeon?


If you’ve been in the hobby for a bit you’ve probably come across geomorphs. They are often cards, tiles, or dice that have bits of dungeon on their surface with pathways running off on each side. That means you can put together two or more geomorphic and be assured they will line up and not cause problems if you keeping adding in more.

I wanted a similar execution for my my personal infinite dungeon. Each side of the page should have two exiting corridors that can be used as entrances/exits to the dungeon and connections to a new perspective of an otherwise same dungeon. With eight equidistant exit corridors I could simply rotate the dungeon 90 degrees and attach it to the current layout to easily double its size. And I would be able to twist the dungeon and keep adding to it ad nauseam.

It’s the geomorphic approach to this design that makes it an INFINITE dungeon. Now, do I WANT to run it as a full campaign mega dungeon, no not really. But, it’s nice to know I could if the need/want arises!

Two-sided Form Factor & Laminated Sheets

Longtime readers know I’m a bit of an analog Dungeon Master. It’s not that I dislike digital tools for prepping and running the game, simply that I think the bells and whistles often cause more of a distraction than they intend. The idea that I could anywhere, anytime, run a nearly infinite dungeon in D&D without WiFi is a powerful feeling.

In the original design I considered making a double-sided map document with one side being an artificial (constructed) dungeonscape and the reverse being a natural environment. What I learned quickly into the process was that was unnecessary. Rarely when I run do I actually map out the dungeon 1:1 on a grid for the players. That means I have a lot of wiggle room in both the size and shape of chambers, and the orientation and snaking of connecting corridors.

Thus, a straight corridor of dressed stone that ends in a T intersection can be a somewhat bendy natural passage that ends in a more natural Y intersection. Perfectly square chambers becomes roughly circular caverns, etc. If I treat the illustrative map and everything that goes with it more like a guideline than hard rules, it becomes much more flexible.

Treated Like Guidelines Rather Than Rules for Making an Infinite Dungeon

Besides, saving one side of the document means I can add useful roll tables and other improvising tools to help me use it better!

As noted, I decided early on that I wanted physical sheets to add to my DM binder. My first thought was lamination and it serves a few purposes. First, it will make the sheets far more sturdy for use in games over months and even years and surviving my DM binder. Second, it allows me to make notes directly on the dungeon. These notes are critical if the session ends in the middle of crawl. And, I don’t have to worry about smudging or tearing the sheet by erasing. I don’t need to worry about Mountain Dew or beer spills either.

But most importantly in my mind, laminating the sheets means I can easily black out areas of the dungeon map. This means I can make alterations to the dungeon directly on the map and makes the dungeon infinitely more unique and difficult for my players to guess the layout when I can “delete” passages and chambers with a simple swipe of a marker. Perfect when I just want to slot in a 5 Room Dungeon to tide my players over until the end of the session.

Asymmetry, Variety, and the Z-Axis

As noted, one of my biggest sticking points with Mentzer’s Basic D&D dungeon is its symmetry. Maybe you would file this under “telegraphing” in the OSR community due to the dozen-odd secret doors that litter the dungeon. But, I’ll go over that specific niggle in a later section.

Dungeon asymmetry serves two things in my mind. First, it makes it difficult for players to deduce where things should be in the dungeon. Second, asymmetry makes it more difficult to get lost in the dungeon because the passages and chambers are more unique. When I look at the Mentzer Dungeon I can easily imagine myself as a PC getting turned around with the high number of similar chambers and layout. Not a massive concern but worth noting.

In my creation, I want plenty of recognizable dungeon chamber shapes in the square, rectangle, etc. but I also included some more unique “dog leg” and cruciform chambers to play up the variety and ensure a level of distinctiveness to both make the dungeon more fun to explore and interesting to ponder why the chambers are that shape.

I also sought to include some corridors that go under/over others. The z-axis is often overlooked in dungeon design, especially small dungeons. But, having some limited verticality makes the dungeon more interesting and can give the party’s mapper a small fit when they find passages doubling back but not intersecting where they’ve mapped explored passages in 2d. In general I would have fully separated levels in a larger bespoke dungeon, it’s a level of complexity that isn’t useful for this project and would greatly increase the amount of space needed to illustrate such a dungeon.

Multiple Exits and Paths

Great dungeons have more than one exit. They make it much easier to accommodate monsters moving in and out of the dungeon without coming across the PCs. It creates a suspension of disbelief that when a room or passage is cleared that it will remain cleared for the rest of the delve. Luckily, making the dungeon geomorphic means there is an easy way to have eight or more distinct ways in and out of the dungeon.

Another great Jaquay dungeon tip is to create looping paths. The Mentzer Dungeon has this as well. You can easily see three easily apparent, interlocking paths that the party can follow that would lead them from the dungeon entrance to its exit. These are nice because it provides you the opportunity as a DM to place meaningful choices and workarounds for challenges in the dungeon. Players can’t figure out the puzzle in one room? That’s fine, they’re not stuck. They can backtrack and take another path that will eventually lead them around to the other side of the puzzle room.

No Chamber Contents, Dungeon Dressing, or Doors

Each chamber and passage should be a basic blank space. While lamination allows me to make subtractive changes to the dungeon and its layout, creating a blank palette allows me to make additive changes. Whether I want pillars, statues, altars, galleries, etc. I can simply drawn them onto the map with a marker. I can even split larger rooms into smaller adjoining rooms. Keeping it blank means I the most amount of freedom to edit the layout of the dungeon on the fly.

It also means I can stock each room with whatever contents and dressing I like, which helps to keep things fresh and useful for delves with PCs of all levels. One of the problems I run into with premade maps are things like secret doors, rubble, chasms, pit traps, etc. where I might not want to include those things for this specific delve. In a premade map that means I have to remember that those features, while on the map, don’t exist when describing things to my players. That’s a lot for my human brain’s RAM to keep loaded. I find it easier to just add things as I want.

And yes, that means my dungeon map has no doors. Instead I’ll add the door roll tables from my Dungeon Creation document to the map’s flip side. That way I can plop down different types of doors, secret or not, in whatever spot I like! Again, this helps to ensure each time I run this dungeon it’s going to FEEL like a brand new, completely unique dungeon. I just don’t need to spend time making it from scratch.

Reverse Side Contents

By reducing the map to a single side of one piece of paper I have plenty of room on the reverse for tables. These tables work together with those I already have in my DM Binder. Together they will make it easy to completely stock a dungeon at the table. Who knows, if I’m feeling daring I might just let the players be the ones who roll on the tables and I can interpret their roll results in real time!

Below is a list of the roll tables I intend to add to the reverse side.

Supplementary Roll Tables

  • Chamber Contents
  • Dead Ends
  • Door Status
  • Door Type
  • Dungeon Dressing
  • Hazards & Obstacles
  • Monster Preoccupations
  • Treasure Location & Status
  • Tricks & Traps

It’s pretty robust. I’ve used these tables to stock plenty of dungeons and feel confident in the results they produce. I have little apprehension in including them for use at the table to prepare a dungeon. I didn’t include my formula for calculating the average number of rooms per session, but I can always rely on the silver standard estimate of ~45 minutes of table time per dungeon chamber for a standard-sized D&D group.

Should we take a look at the current iteration?

The Red Ragged Fiend Infinite Dungeon for D&D

I did end up going with the laminated sheets. It makes the dungeon easy to use with permanent and erasable markers, a big bonus in my opinion. I laminated the dungeon sheets using a home lamination machine and it worked great to my surprise. I even ended up taking the Infinite Dungeon sheets on vacation with me to tool around with in my hotel downtime and had zero issues.

The front sports the geomorphic dungeon map on a grid with empty chambers and passages as intended. The reverse side holds the tables for reference while building/running. One thing I quickly realized is the map works even better if I have two of the sheets. It makes it easy to stick them together allowing play to smoothly transition from one geomorph sheet to the next without getting confused. An unintended benefit was I was able to make the tables much larger on the reverse side, splitting them between two sheets.

I took the laminated prototypes pages on vacation with me to test them during downtime in the hotel. The easiest way I found to stress the concept to see how it would act is by making some short (1-2 session) dungeons in different orientations and random filling. And… it went surprisingly well. I found the results to be quite similar to the handcrafted dungeons I would normally make for a game. The most significant difference between these off-hand dungeons and one of my normal creations was the layout/design philosophy, which was expected.

I’m generally a proponent of tight dungeons that don’t have a lot of strange winding paths or passages with dead ends. I also tend to have a very centralized dungeon design with the more important and larger chambers central to the overall complex. The results were also flatter, lacking distinct dungeon levels or thematic zones. Again, not differences that bother me when it comes to pulling something from my back pocket to run a session or more of dungeon delving. Moreover these design hangups are my own personal ones. For Game Masters and groups that enjoy gonzo dungeons and their weirdness I suspect it would work even better!

One aspect I was very impressed with was the foresight of making two sheets that could be used together. It greatly expanded my options when creating the small dungeons as I could straddle a dungeon across two, even three, different geomorphs. I also quickly realized that if I chose to offset the passage connections between geomorphs I could use the other (the dead end) as stairs to upper or lower levels of the dungeon. This realization relieved one of my biggest concerns with the Infinite Dungeon layout, that it didn’t support multi-zone/level delving. So the Infinite Dungeon concept is actually infinite and if I wanted to, I could create a classic BECMI or Basic D&D 1-20 level dungeon!

On the downside, I did find the right angles of the map did lead my creativity towards dressed stone construction rather than natural environments. But, I think practice using the Infinite Dungeon framework and leaning into the winding passages and dead ends will help smooth out those wrinkles. It will also help when I’m using the Infinite Dungeon to represent a specific place in a game instead of white room theory crafting. When I’ll have to make the dungeon be a natural cave complex it will make it easier to adjust the dungeon layout and descriptions so it FEELS like a natural environment.

Overall, I think the Red Ragged Fiend Infinite Dungeon for D&D is a rousing success!

I do my best but concepts like these are often better understood by showing you and not telling you about it. I plan to go over the Infinite Dungeon in an upcoming live stream, showcase what it can do, and illustrate how it works. So, if you’re interested in a better visual make sure to follow RRF over on Twitch! Right now we’re streaming actual play solo RPG content and DM/GM discussion topics.

And, if you miss a stream don’t worry. All the stream VODs are saved over on the RedRaggedFiend YouTube channel. You can always subscribe there to watch the videos at your leisure and never miss out!

Final Words on Crafting an Infinite Dungeon for D&D

Again, I’m just so pleased how well everything worked together. Looking back over the dungeons I cobbled together on vacation, I would put them squarely middle-of-the-pack for most one-page dungeons and adventures I’ve seen online. The Infinite Dungeon is a great experiment to try for yourself. I think it will help myself and other DM/GMs see how much gameplay we can pack into the endlessly versatile dungeon space.

And maybe best of all, this concept will work for every edition of D&D, Mentzer Basic D&D to 5e, Pathfinder, or whatever TTRPG you prefer! Since everything about the dungeon’s concept is versatile I could easily see a creative Game Master use this concept for non-fantasy RPGs as well, like winding alleys of a dystopian city for cyber punk gaming, etc.

I’m really champing at the bit to try this out at the table. As an analog-leaning Dungeon Master, my only personal weakness would be stocking monster encounters on the fly. But for those of you who use digital tools to run your games that’s a non-issue. And even if I had the books in front of me and a five-minute recess I could easily stock one of the small dungeons I created. More than enough gameplay to carry me to the end of the session!

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