Building a random dungeon with the 5e DMG

Let’s say you don’t want to use an existing dungeon generator for some reason. Maybe you have some time to kill in a parking garage and can’t reach the Internet. Maybe you want to draw a map but nothing comes to mind. You could do worse than use “Appendix A: Random Dungeons” from the D&D 5e Dungeon Master’s Guide.

In this post, I’ll generate a dungeon to go with the adventure I created using the same book a few days ago. That means we need to create a lair originally built by dwarves under a graveyard. It should have some bells that contain the villain’s soul, or at least will summon a good celestial.

Many talented illustrators work on maps for roleplaying games. Professionals like Jared Blando and Mike Schley set a really high bar, but amateurs often do a fine job as well. I do not belong to any of those august groups – just a nerd with a #2 pencil, some graph paper, and dice. That explanation out of the way, let’s roll on the Starting Area table:

9. Passage, 10 ft wide; T intersection

That doesn’t mean the party magically transports into this place. “Pick one of the doors or passages leading into the starting area as the entrance to the dungeon as a whole.”

I’ll roll three times on the Passages table to see what connects here, then figure out where to put the entrance.

7. Continue straight 20 ft, side passage to the right, then an additional 10 ft ahead
13. Continue straight 20 ft, then the passage turns right and continues 10 ft
3. Continue straight 20 ft, door to the right, then an additional 10 ft ahead.

I need to roll a passage width for the side passage on the first roll. Also, I want to use that door on the final roll as my entrance. So on Passage Width:

5. 10 feet

Then Door Type:

11. Wooden, barred or locked

I don’t need to roll for what lies beyond the door in this case. Four more rolls on the Passage table:

13. Continue straight 20 ft, then the passage turns right and continues 10 ft
10. Continue straight 20 ft, comes to a dead end; 10 percent chance of a secret door
17. Chamber (roll on the Chamber table)
2. Continue straight 30 ft, no doors or side passages

I will put that dead end at the north, the chamber on the west, and the two passages heading east can use the other rolls. No secret door (6 on a d10) and the chamber is:

14. Rectangle, 40 x 50 ft

I will come back to that chamber in a moment. First, two more passages:

18. Chamber (roll on the Chamber table)
6. Continue straight 20 ft, side passage to the right, then an additional 10 ft ahead.

The chamber will go in the northeast corner and I need a width for the side passage.

11. Rectangle, 30 x 40 ft
5. 10 ft

We require two more rolls on the Passages table. Clearly that one is the workhorse of the process!

6. Continue straight 20 ft, side passage to the right, then an additional 10 ft ahead.
7. Continue straight 20 ft, side passage to the right, then an additional 10 ft ahead.

Widths for these:

4. 10 ft
8. 10 ft

However, we need to start thinking about how this starts to run into limits. From the introduction to the appendix:

Following these instructions can lead to sprawling complexes that more than fill a single sheet of graph paper. If you want to constrain the dungeon, establish limits ahead of time on how far it can grow.

The most obvious limit to a dungeon’s size is the graph paer it’s drawn on. If a feature would exceed the boundaries of the page, curtail it. A corridor might turn or come to a dead end at the map’s edge, or you can make a chamber smaller to fit the available space.

Alternatively, you can decide that passages leading off the edge of the map are additional dungeon entrances. Stairs, shafts, and other features that would normally lead to levels you don’t plan to map can serve a similar purpose.

For the purposes of this post, I want everything to fit on one sheet of graph paper. So that means that my next set of rolls may need a bit of adjusting. Already, I had to close off a passage because it had turned back on itself and we had a conflict. That passage could also ramp above or below the other passage. However, I have enough trouble with two dimensions. Adding a third complicates things too much now.

10. Continue straight 20 ft, comes to a dead end; 10 percent chance of a secret door. [rolled a 2, no secret door]
20. Stairs (roll on the Stairs table)

For the stairs, I could also reroll, use it as an alternative entrance, or replace them with another feature. As noted, I don’t want to go up or down. So I will choose to place another entrance here.

What about our two chambers? We need to roll for the number of exits first. The Chamber Exits table has one column for Normal Chambers (including the 30 x 40 ft room), and another for Large Chambers (including the 40 x 50 ft room). Respectively:

15. Two exits
9. Two exits

For each exit, we roll Location and Type.

17. Wall right of entrance + 7. Door + 2. Wooden + 9. Chamber on the other side
9. Wall left of entrance + 4. Door + 16. Iron, barred or locked + 8. Passage 20 ft straight ahead + 9. 10 ft wide

15. Wall right of entrance + 4. Door + 1. Wooden + 9. Chamber on the other side
20. Same wall as entrance + 14. Corridor, 10 ft long + 13. 20 feet wide

One of the passages has to end there because it has reached the edge of the paper. We still have two chambers and a passage, though.

13. Rectangle, 40 x 50 ft
12. Rectangle, 30 x 40 ft
11. Continue straight 20 ft, then the passage turns left and continues 10 ft.

That passage will end there as it has run back into a wall. Each chamber should have four exits, but at this point I think we have enough for our dungeon. This includes four full-size chambers and a side room. Just for demonstration purposes (like this whole thing), I will roll twice on the Chamber Purpose table for lairs and then three more times for General Dungeon Chamber:

17. Training and exercise room
7. Cistern or well for drinking water
28. Crypt
61. Observatory
80. Storage room

Other dungeon types like Planar Gates and Strongholds have their own tables. Additional tables include things like Current Chamber State and Chamber Contents. This latter table can then direct you to Monsters & Motivations, Random Traps, and more. For example, in the Cistern room, I could decide it remains in working order but roll on other tables to learn that it is an otherwise empty room with spider webs.

By rolling on the various Dungeon Dressing tables, we also learn that people in the dungeon may hear footsteps ahead of them and breathe clear, damp air that smells of manure. Rotting wood pieces litter the floor. The crypt may contain furnishings like vestments, a stand, and a throne.

Hopefully this gives you a sense of what these tables can do. In real usage, I would probably interpret the rolls a bit more liberally (“training and exercise”, really?!) and develop out the rooms a little further. But for now, our little dungeon looks like this: