Tuesday, September 25, 2018

Stocking the Megadungeon

Today, I am going to work out just how I stock my dungeon. I’ve been drawing like mad, and I think I should probably start filling in some room content before pushing too deep. That way I can do a second pass on the map and add in more details, modify rooms where appropriate, and generally polish the bits players are likely to see early on.

What do I want from my stocking method? Well for one, I want empty rooms. I want a fair number of empty rooms, actually. But let’s be clear: empty does not mean uninteresting! It just means there isn’t an encounter in it. There are a couple of reasons I want a lot of empty rooms. For one, if every room has an encounter, the dungeon becomes somewhat homogenous and therefore predictable. Megadungeons are all about variation and weirdness, so let’s keep it weird. Another is that it feels more natural. You don’t find people in every single room of every building on Earth, so why should you find monsters in every room underground? But my main reason is that it builds tension. Is this door safe? Does certain death lie in wait just beyond? Maybe we will finally find a temporary haven. Or even better, a treasure horde! Let’s find out!

This plays heavily into the exploration aspect of megadungeon play. If players know there is a monster or trap in each room, they will expect it, and they are merely killing things to map the dungeon. That’s not really exploration as much as it is a slog. With the variety that empty rooms add, the megadungeon becomes even less predictable, so the sense of discovery is heightened.

So how empty do I want my dungeon? I’m thinking one third empty sounds about right. That means that one third of rooms won’t have any monsters or traps. They might have treasure or maybe just dusty shelving and a rotting desk. Or maybe nothing at all. No matter what, they will still get interesting contents or descriptions. Nothing is worse than finding a nondescript, empty 30x30 room.

That leaves two-thirds of the rooms to actually be stocked with something worthy of the moniker “encounter”. In my experience, that means one of monster, trap, or puzzle. Of these, I personally dislike puzzles the most, so I will weight those to be the fewest. I’d rather not pit the players’ intellects against my own ability to create puzzles I find clever but will likely annoy and frustrate them, so let’s minimize that. I do like traps and monsters, though, and of these, I probably like monsters only marginally more. Unfortunately, a heavily trapped dungeon tends to annoy players and grind the game to a halt as they search every square inch for hidden death. That’s why I’m going to weight monsters most heavily, followed by traps, and then in last place, puzzles.

Giving some thought to proportionality within encounters, I think I’d like to see twice as many traps as puzzles. That will make the few puzzles that do pop up more special. I also want more monsters than traps, but by how much? Again, I think about twice as often sounds good. This means if there is an encounter, the players have a 67% chance of it being a monster and a 33% chance of it being a trap or puzzle, and if it’s not a monster, there’s a two-thirds chance of it being a trap and not a puzzle.

At a glance, that looks good, but I have done something Not-Good. I have ignored combination encounters – those wonderful rooms where players have to contend with traps and monsters at the same time. Or maybe traps and puzzles, or well, you get the idea. So let’s break this down a little more. In a 100-room dungeon, 33 will be empty, and 67 will have something. Of the 67, two-thirds of those (or 45) will be monsters, and the remaining 22 will have either a trap or a puzzle. Of those 22 rooms, 15 will have traps and 7 will be puzzles. That gives the following breakdown by percentage:

  • Empty – 33%
  • Monster – 45%
  • Trap – 15%
  • Puzzle – 7%

This does add up to 100%, so it appears I did my math correctly. Let’s analyze this some more. There will be roughly 50% more rooms with monsters than empty rooms, and three times as many as with traps. There will be about half as many rooms with traps as are empty, which sounds pretty good; we don’t want players to expect traps in empty rooms. There are very few puzzles. Good. So, if you open a random door, there’s about a fifty-fifty chance of seeing a monster, and a two-thirds chance that you are walking into some kind of interesting situation. I like this.

But If you notice, I still haven’t addressed combination encounters. I just made up some probabilities. But that’s what will enable this to get good. I can now roll three times on a random number generator to determine if a monster, a trap, and a puzzle appears in a room. Each has an associated chance to appear at all, independent of the others. If none appear – something that should happen one third of the time – the room is just empty. If I were to do this manually, I’d want 3d% to make this easy, but for GURPS people who demand d6s, your values are as follows: 8-11 for Monsters, 3, 7, 14, 18 for Traps, and 5-6 for Puzzles. Yes, that’s messy; that’s why I’m using three d%s or a random number generator.

And that’s how I will be stocking my dungeon. After I do a hundred rooms, I’ll take a look at the results and decide if I like them and adjust my percentages from there. And the best part of using a random number generator is that I can do batch runs, look at the results, and tweak one file. Once everything looks good, I can run off thousands of rooms in a matter of seconds.

What stocking methods do you use?


  1. I work with a little more empty space. Part of my megadungeon is a sewer system that uses caged otyughs for solid waste management. There are frequent encounters with surface driven maintenance workers, with deep subsurface maintenance teams (surgically modified goblins, siege beasts and representatives of the controlling parties) several enclaves of mixed troll folk, wandering slorn, undead that were bricked off, and flocks of scavenger types, aling with a lost city of elder things...

    1. That sounds like a heap of awesome. I'm still waffling a little on the exact amount of empty space. Since this particular dungeon isn't visited regularly (yet), I can probably justify less empty space at first, but I am going for a little bit of an 'abandoned' feel for the upper levels, so I might tweak the stocking for that. I'm sure once I write my dungeon stocking generator, I'll get a better feel and tune it.

    2. In the end (as you'll see in the next post), I ended up going with about half empty after looking at the results.