I started a low-pressure megadungeon. It’s the opposite of Dungeon23: I don’t have to do anything on it if I don’t want to, but if I’m stuck on something else I can go and just fill out a room or a faction or add an encounter or something. It feels a lot more feasible to me. It’s inspired by some of the same stuff Gus L wrote about here, through coincidence (I’ll refer back to that a few times).

But, never content to let my mind be at ease, I realised…if it’s a megadungeon, perhaps some of the principles I thought about in Elden Ring and Overworlds apply, too, in an Underworld? Like, we have Tears of the Kingdom’s Depths to see a digital example of how it’s exactly the damned same, and while I can’t find a database that documents the depths, it’s basically all monsters, with only a handful of other points of interest at all.

Megadungeon Density

Ok, the density information will have to be translated. This is a megadungeon, but if we’re treating it as an overworld after the model of Elden Ring, then we need to remember that the dungeons here aren’t dungeons (because the whole thing is the dungeon), we’ll call them sublevels. We’ll chunk it into Sets, where a collection of sets contains:

• Five scenes: High uniqueness, low complexity, low hostility. ▲U/▼C/▼H
• Five lairs: ▲U/▲C/▲H
• Two or three sub-levels containing traps, exploration and puzzles: ▲U/▲C/▲H
• One dungeon merchant or other utility (blacksmith, sage, trainer): ▼U/▼C/▼H 

Ok, this is interesting. It gives us a little insight into those early Legend of Zelda dungeons, which had merchants in them. This is why this makes sense structurally. There, they were hidden: It makes sense that utilities be hidden in a hostile space. Also, there are some implications: Outside of sublevels, the megadungeon doesn’t have the same density as a traditional dungeon, which follows roughly a formula of 2 empty rooms: 2 monster room: 1 trap room: 1 special room. This works for the sublevels perfectly, as it proceduralises the complexity. Sublevels should be unique!

The Betwixt

What does the megadungeon look like outside sublevels, then? Let’s call it the Betwixt. Well, we have two options. We come up with a second formula, or we use something like Bloggie Award-winning Flux Space to abstract the Betwixt. Both of these are cool ideas, but I feel like using Flux Space is too big a goal for a design sketch here, and a formula for the Betwixt is actually staring us straight in the face.

The Elden Ring map is 30 square miles. If you break it up into chunks that are equal with your vision to the horizon, that’s 300 chunks of map, or I’ll call them 300 lines of sight. In a dungeon, they’re rooms, right? Or potentially, areas where you can see into adjacent rooms.

How many of these lines of sight contained stuff in Elden Ring? Per line of sight, we had 2-in-6 chance of a dungeon, 3-in-6 chance of a lair, 3-in-6 chance of a scene, and 1-in-6 chance of a utility (actually, a slightly higher chance of utility, but I’m liking the cleaner probabilities). These can translate directly across to the Betwixt as a d12 roll: 1-2. Dungeon; 3. Utility; 4-5. Lair; 6-7. Scene; 8-12. Empty.

Let’s compare Sublevels and the Betwixt to get a sense of the difference in complexity:

There’s quite a difference there in terms of complexity! That’s what we want to see. We have roughly 20% more hostility in the Sublevels than the Betwixt, and that will justify the increased reward.

How many rooms are there in the Betwixt? If we assume areas are lines of sight rather than rooms, you’ll max out at 4 connected rooms normally, so let’s call it average and say there’ll be 300 lines of sight in the Betwixt, consisting of roughly 2 (1-4) rooms each, excluding sub-levels, so between 200 and 1200 rooms, probably 600.

Building the Megadungeon

So, how do we use this to build a megadungeon? For the whole megadungeon, we need to know:

• Why is my megadungeon hostile to visitors?
• Why visit the megadungeon if it’s hostile to you?
• Where is the town? Is it at the surface, or in the dungeon?

We don’t have to decide exactly where the town is in the dungeon if it’s there (maybe we just roll 1d6 each time we find a utility, and replace it with a town on a 6 the first time we do it), but we need to know if it’s in the dungeon. I’d recommend adding another town if we increase the size of the megadungeon beyond 300 lines of sight, as well. Our procedure will be:

1. Generate Betwixt (until we roll Sub-level)
2. Interrupt to generate a Sublevel (according to standard dungeon creation procedures, I wrote about one here, and plenty of other great procedures are out there like this one and this one and I’m certain Gus did a fire one as well) (add; Gus did! it was nominated for a Bloggie!).
3. Repeat

There are some things missing here, namely changes in elevation. Honestly, I’d probably just roll for a change in elevation every line of sight, because it makes sense to me for megadungeons to be a mess. Or, you could choose to have a broad flat megadungeon. Or, you could choose an arbitrary number of rooms per level; I’d recommend between 20 and 60 rooms per dungeon level, the lower number being the less traditional.

Sub-levels

Wait, but what characteristics separate a Sub-level from the Betwixt? In Elden Ring, they’re underground, but in a megadungeon that’s not the differentiator. I’ve got some ideas:

1. Traps and puzzles found in greater quantities in sub-levels.
2. Treasure is found in greater quantities in sub-levels.
3. Sub-levels each have a unique visual or sensory theme.
4. Sublevels are connected out of phase with the rest of the megadungeon.
5. Sublevels have a unique ecosystem.

I think most of these are self-explanatory. They can’t hold all the treasure or puzzles because that limits the possibilities for scenes. But most of it, certainly all the gold. They have to be readily recognisable from the Betwixt and from the other Sub-levels: “The Underwater Dungeon” or “The Lava Dungeon” or “The Fungus Dungeon” or “The Eyeball Dungeon”. Their NPCs or monsters should feel encapsulated, probably related to the theme, and have a faction or factions all of their own.

The fourth point though, is important: Sublevels are both connected and disconnected from the Betwixt in surprising ways. They are the source of our loops. So, have them vertically between levels of the Betwixt, have them underneath the betwixt or above it, have them half between two sections of the Betwixt, or inaccessible from one. Have them lead from one area to another. They are our shortcuts deeper and our shortcuts back. They help us make sense of the labyrinth that is the Betwixt.

Wandering monsters

Ok, so our wandering monsters need to reflect this. Gus’ article also talked about this, the early example dungeons had multiple encounter tables for each level. I’m, not going to beat around the bush with that, but it’s a megadungeon, so we need a decently large encounter table, and we can use that to our advantage. So we’ll give each Sub-level a 6 item wandering monster table with equal chances of each encounter in the Sublevel, but structure it so that the rarest encounters in the Betwixt are at the bottom (i.e. rarest is item 6, but number them 6 to 12, trust me). Then, we build 5-item Betwixt wandering monsters tables, according to dungeon level (or whatever criteria suits your Betwixt design) and then put the rarest encounters are at the bottom (i.e. for this one, item 1 is the rarest). Whenever you’re in the Betwixt, you paste them together and roll 2d6. When you’re in the Sublevel, you only roll 1d6 for Sublevel wandering monsters.

Sublevel Size

The one remaining consideration is sublevel size. How big should a sublevel be? Is probably go back to the same 20 to 60 room hallmark, but it would be cool to vary it for surprise, particularly if we harken back to the predictable entrances principle: If we can identify our sublevels consistently, or even lay them out in similar ways using similar themes, we can use the expectations of the player characters to surprise and subvert them.

Classically populated rooms are quite sparse of monsters, and really rely on Wandering Monsters to make up their populations, so I’d scale the size of the room up based on how many cool ideas you have: You have three cool traps, you’re aiming for eighteen rooms. You have eight cool monster encounters, you’re aiming for twenty four, etc.

Polishing up and finishing off

So, there are a few things missing from this procedure. I suspect I’d use Warren’s Punnet Monsters to populate the wandering monster tables. We need to pick an overall theme for what the Betwixt is. We need to figure out how we’ll structure the Betwixt, because that will inform how our Sublevels are generated. And, of course we still, no matter how much theorising we have to do, write a boatload of dungeon keys.

But, that’s my thought processes in how we could build a megadungeon. I feel like it’s cool, because unlike anything else I’ve seen, it means that we can write it and map it in discrete chunks, of as little as 4 lines of sight or a maximum of 16 rooms.

I’d love to hear ya’ll thoughts about this. This is wild dungeon design, and I’m pretty excited about it.

Idle Cartulary