Undermountain is a large module, a mega-dungeon, placed below a seaside metropolis called Waterdeep in the Forgotten Realms. The original boxed set (including the first three levels of the dungeon) always fascinated me, partly because it was the only mega-dungeon I had read.

The level maps are on poster-size paper, the squares representing 10′ of space are tiny. It’s really quite large. That’s one of its problems. The DM can’t hide the map (which does show secret areas and such) and it’s hard to handle behind the screen. I’ve seen one DM use black construction paper to hide sections of the map from players but that doesn’t hide the secret doors and marks in the keyed rooms.

That’s a second problem: the dungeon is not entirely filled-out. The central, or core, areas are detailed but the outer areas are not. Only about a tenth of the dungeon’s space is keyed. And these outer areas are often bland or stupid-looking, as if the cartographer just needed to fill up the space with something and it didn’t matter whether it was good or not.

But Undermountain drew me in because of its promise. It was not a dungeon you could clear out, or “finish”. It was just too big. And it had a reputation. And it could contain everything from horror to whimsy because of its background.

So I decided to make my own version of Undermountain. Not only to make my own maps and rooms, but to change what was already there so people who had played it before would discover pleasant (and some not so pleasant) surprises. I decided I needed an outline for each level, level maps, random encounter charts, and room descriptions. And then it would virtually run itself!

Internet Research followed. For a DM, Internet Research is a cunning euphemism for “finding someone with ideas and stealing them”. I’m not publishing this turkey, why should everything come from my head, right?

My outline gave me some cool ideas for Level 1 all the way down to Level 7. You might not think much of this, only seven levels, but the levels were widely spaced and there would be sub-levels between. In all, we’re talking about a depth of 2100 feet. The outline also defined the size of a level. I decided to base my level size on 4 square per inch graph paper, 8 x 11 inches. 10′ per square. So one sheet would cover 32 squares by 44 squares. Each level was five sheets by five sheets. They were labeled like Excel cells, with letters across the top and numbers down the side. Each section had multiple connections, many secret, to neighboring sections. I drew sewer grate style small tunnels between rooms, water pipes, etc. The dungeon was 1600′ by 2200′ per level. Almost a square mile of mapped 10′ squares not counting sublevels, of which there could be 2-3 between each pair of levels taking up one map page per sublevel.

The original Undermountain Level 1
(The original, 155 squares across)

25 page (5x5) DM map of Undermountain level 1
(Mine, 160 squares across)

Lots of mapping. In MS Paint. Each 10′ square was 18 pixels across plus a 2-pixel border. A square owned its side of the border, so effectively each square was 20 pixels wide unless there was a wall. Walls were a full 2 pixels wide. Ledges were only one pixel wide.

I actually made it through mapping Levels 1-3 and then started keying rooms. The core rooms I mapped closely to how they appeared in the boxed set. Their descriptions were slightly altered. For example, in the hall of mirrors, instead of expecting someone to come by and fix the mirrors occasionally, I had the shattered glass melt and evaporate and the frame grow new glass like it was a sheet of crystals. And the space behind the 10′ square frame was a 10′ cube room which could hold just about anything. It was a pretty tight little ambush room, though they never got ambushed in it. Oh and one randomly-shuffling mirror at a time would grow a Mirror of Opposition and another would grow a random magical mirror, which might be beneficial if you looked into it.

Anyway, my Internet Research scrounged up one excellent resource. A guy (I know, [Citation Needed], right?) had detailed many of the rooms on the original Undermountain map for Levels 1 and 2. Many of the room descriptions were too transient and were more like encounters, so I tore them apart and used ideas for my encounter lists. But many were good tricks and ideas.

I found a riddle forum that was an excellent source of inspiration for tricks and traps. various netbooks, mostly full of dreck written by simple folk, but with some gems. Architectural sites, news articles, travel documentaries, etc. It was all fuel for the growing monster that was Undermountain. And of course every thing I came across sparked some little bit of inspiration in me. I was carrying a notebook at the time and would jot down anything interesting.

So it came time to actually choose which rooms would be keyed to which descriptions. The Word doc holding my rooms became too slow to open and save, so I split them up by level. That held off the inevitable for a short time. I realized that my numbering scheme of 122 for Level 1, Room 22 wouldn’t work because I had far more than 100 rooms per level. I decided number/letter for the level and for the two-digit room code would be enough for the levels (1-9 then A-Z giving me 35 levels) and for the rooms (Room 34, Room A9, Room ZD, etc. giving me something over 1,000 rooms per level).

I keyed about a third of the rooms on Level 1 and a quarter of Level 2 and 3 each. It was important to me that there be empty spaces between exciting adventure rooms. I mapped but did not key in about half of Level 4 and small parts of Level 5. But I had plenty of room descriptions that I wanted to put there eventually.

So why did it abruptly stop? It was every other weekend swapping with another campaign, some players could only play every other week, and they wanted to play in the other one. Partly because I was running it as a playtest of an earlier version of Game XYZ and they didn’t enjoy it as much.

(It was entirely feat-based, classes gaining a feat every level, but almost all feats could be taken up to 5 times for broader and more intense effect)

So lesson learned! Make a simple playtest module and let them concentrate on the system for a couple sessions instead of the adventure. Not a dungeon with 60 pages of terse 10-point text for Level 1.

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15 Responses to “Undermountain”

  1. Greg Says:

    Well, I’m friggin impressed. Undermountain has been on my mind lately. A friend has offered to donate his old boxed set (plus the Lost Levels) to my D&D group, and I was considering just how much out-of-the-box work it would require.

    You should really consider offer your fleshed-out, revamped Undermountain as a zip. I, for one, would be willing to Paypal some cash for something like that.

    Have you checked out 0one’s “Dungeon Under the Mountain” PDFs?


    Genericized PDF version of Undermountain BUT requiring a lot of fleshing out by the DM.

  2. 1d30 Says:

    Unfortunately, the text is very kitchen-sinked and I simply don’t remember what I invented and what I stole from someone else. Perhaps half the ideas are completely me. In I’d say 95%+ of borrowed cases I rewrote it in my own words. But what I ended up with is still well within the confines of plagiarism. I wouldn’t be comfortable selling it.

    And in addition I don’t even remember who to credit. I didn’t keep notes on where I found inspiration or outright stole room ideas.

    I understand that there’s nothing new under the sun. Every word writ is a theft. But admitting that hardly clothes said naked villainy.

    On the other hand, I wholeheartedly encourage DMs to steal left and right for their games. We’re trying to entertain and be entertained. I just get careful when money is about.

  3. Greg Says:

    Ah, that’s a shame, but I totally understand. I borrow from various sources to put together dungeons. It’s the nature of the beast!

  4. Samuel Plahetka Says:

    you could always put a legal type statement on it thanking those you remember and apoligizing to the people you do not, along with a note saying if anything you wrote is within, to give you a message so you can add their information or if they don’t like that it’s there a remove my stuff thing too. That should cover you. As long as you don’t charge that is. So when are we gonna see it?

  5. Capt_Poco Says:

    That bitmap looks amazing!

    Please release your DM notes! Obviously this couldn’t be something that you sold, but it would be an amazing contribution to the RPG community. It’s not every day that someone makes something so colossally awesome.

  6. 1d30 Says:

    I’d be more likely to rewrite everything so as to distance it further from the original ideas, and publish it as a separate Dungeon What Is Totally Not Undermountain.

    Also the lower levels didn’t have black spaces around the corners. I originally wanted to have a more organic circular look but it’s just a waste of opportunity.

    And I need more interconnectedness. More secret things. More passages that are hard to use and are worth going around. It’s in a form that I’d feel good about DMing but it’s not something I’d publish as-is yet.

    • samuel plahetka Says:

      Hmm. I have a few older projects that need massive revision and people have asked me to release these and a weird non-writing life. If you want to do a send each other our progress for the day type thing or however.

  7. Bevan Says:

    I’m re-looking at undermountain- any chance of privately emailing your maps/notes through? I would obviously agree to not utilize ANY of your material other than at my game table. =]

  8. 1d30 Says:

    Nope. But this is a project, and one that develops even when I’m not directly working on it. It’ll see the light of day eventually.

    • Samuel Plahetka Says:

      I’m still way interested in this. If you are willing around the time you release it I can do a short story like the old playsession type stories TSR used to use for examples in part of the dungeon. just to help promote (i can post it to my blog or release it on drivethrufantasy.com)

  9. Bdohazelnutz Says:

    If you are willing to share your work, I would love to look at the map and notes.

  10. 1d30 Says:

    Leaving a reply for Samuel and others who were interested: I think this manner of mapping the dungeon is a bit too dense. Instead of full pages of grid map I think a 30×30 grid of map with notes around it is a better segment size, like the One Page Dungeon stuff. That way you don’t need a separate doc with room descriptions. Also write as much as you can on the map itself.

    I still might do something this expansive, just with smaller sections.

  11. Keighn Says:

    Any progress on releasing that ms-paint image forcomparison?

    • Bevan Says:

      Hi Keighn, man welcome to the far corners of the internet! I flagged this to notify my of new comments eight YEARS ago, so methinks any updates unlikely. If you do find some cool stuff relating to UM feel free to fire it across virtualmagic Gmail dot com.

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