Let’s Build A Campaign Setting: Distance, Travel, and Size

Welcome to the third part in my Let’s Build series, where I’m cataloguing my design process as I build a setting that will be used to house a campaign that will take place over a full 20 levels. If you haven’t yet read the first two parts of this series, you can find them here and here.

This post will be a little unstructured, because I’m writing it as I’m working on this. It’s much easier for me to document what I’m working on as I work on it, rather than doing the work and trying to write it up later, so if I jump from thing to thing, I hope you’ll forgive me. That’s just how I work – at least at this stage of design, anyway.

Before I draw anything, I have to figure out how big this setting needs to be. As I’ve said several times – and cast in stone into my design principles – I want this island to be fully explorable over twenty levels. The first thing to determine, then, is how much ground a party can cover in 20 levels.

Now, it’s obvious that party aren’t going to spend their whole time travelling and mapping this island – there will be adventures to be had in self-contained locations, intrigue and mystery in whatever settlements/towns/whatevers I build, and things like that. As a starting point, though, I decided to work out how big this area can be if the party travel as far as possible every single day they spend on the island, from level 1 to 20.

For this, we turn to two tables. The first is the one that covers travel pace, which you can find on DND Beyond. The rules for overland travel spell out how much terrain is covered moving at a slow, normal, and fast pace (assuming 8 hours of travelling in a day), with rules for Forced Marching – that is, travelling for longer than 8 hours per day. Those numbers look like this:

Distance Covered (miles/day)
Forced March
Pace 8 Hour Day 9 hour Day 10 Hour Day 11 Hour Day 12 Hour Day
Slow 18 20 22 24 26
Normal 24 27 30 33 36
Fast 30 34 38 42 46

For the purposes of determining my maximum area, I’m just going to assume players travel at a normal rate, don’t risk exhaustion (so no forced march), and travel as far as they can each day, without backtracking or revisiting previously explored terrain. In hindsight it may have been better for me to use the figures for slow exploration, to account for things like dungeons and site-based adventures, but it’s not a big deal at this stage. As you’ll see, I’m going to build this thing so that it can be easily expanded or contracted as required.

So, from the table above, we can see that a party travelling at a normal pace covers 24 miles per day. The next step is to figure out how many adventuring days the party undertake between levels 1 and 20. We can do this with the help of two more tables – expected XP per adventuring day (which is on page 84 of the Dungeon Master’s Guide, and the Character Advancement table. I took those two tables and put them together in Excel, figuring out how many days-worth of adventure is needed to level up to level 20 assuming players are gaining an ideal amount of experience, and multiplied that number of days by 24 to arrive at a final maximum area for the setting. In the final figures I rounded up, but again – this is a maximum size, and I don’t intend to fill it completely (as you’ll see).

Using that table we can see that our island needs to cover an area of roughly 3360 miles and will take 140 days to explore completely if the party do nothing but travel.

So, let’s take a look at the sizes of some real islands. The obvious place to start – for me, at least, since I live there – is with mainland Britain. I have a hunch that that will be much too big for my purposes, but it’s a starting point.

According to Wikipedia, mainland Britain is 94,060 square miles. That’s almost 28 times bigger than the setting I’m developing. That’s good to know, because I don’t fancy building something the size of Britain.

So, what about Ireland? That’s 32,595 square miles, which is more than I expected and still ten times bigger than our setting. We need to go smaller.

I could keep doing this through trial and error, thinking of islands and finding out how big they are, but that takes too long. Instead, I can just pull up Wikipedia’s list of islands by area and scroll down until I get into the range I want to be in. And, lo and behold, Corsica (an island off the coast of France) is 3375 square miles. There are a few others in my range, too – Chiloe Island off the coast of Chile, Disko Island off the coast of Greenland, and Carney Island, an unclaimed territory in Antartica.

I’m making a big assumption here – which is that I’ll be building one island rather than an archipelago. I’m also not accounting for players exploring underground regions of the island. Realistically, I probably want to go smaller than the 3300 square miles we know we can fill, for the reasons I just listed and the fact that the players aren’t going to spend all their time travelling. Right now I’m figuring out my upper bounds for size, so that when it comes time to start drawing I can lay out a space and know that I can’t go bigger than that.

And while we’re on that, let’s talk about space. (I told you this post would be a little all over the place – ultimately, this is a log of my creative process rather than something like a tutorial, and this is just how my process works). I may not draw anything this week – at the time of writing this, I haven’t drawn anything, but that may change by the time I get to the end of this post – but it will be nice to know how much space I can fill with my island when I start drawing.

We know that we’re working with a maximum size of 3300 square miles. If I take the square root of 3300 miles, I know how big a square I can fit the island into. In this case, the square root of 3300 is ~57. If we round down for ease, we know that I can draw a 57×57 square and have enough room to fit the whole island inside it. Bear in mind that I’ve already decided I won’t use all of the 3300 miles; that box gives us a total area of 3249 miles. When I draw the island (or islands) I’ll keep all the borders within that 57×57 boundary, which will reduce the area of the islands even more (due to the negative space of the water surrounding the landmasses, which will be included in that 57 x 57 by box to some degree).

There’s also no need for it to be a square. I can take that boundary of 57×57 and hack into it, carving off shapes and realigning them to give myself interesting shapes that don’t exceed our target area. Like this:

I still need to work out things like the story of this island, but I’m in the mood to draw, so I’m going to start sketching some ideas. There’s only so far maths and working things out can take you with a creative exercise; at some point, you need to simply create, and see what happens.

There are a couple of approaches I can take to mapping this thing out properly that I’ll talk about in a future post – things like dividing the map into hexes and assigning days to each one. I’m not going to worry about that at the moment, though, because I’m not thinking about details. All I’m doing is a creative exercise, drawing interesting shapes and terrain features and hoping that something jumps out at me and says “I’m your guy”. These early sketches will be reworked and refined as I develop more of the setting, and the final thing may look vastly different to anything I draw at this stage.

Honestly, I’m just feeling my way through this process at this point, doing what feels right. I know that I want the history of the island to inform the events that are transpiring when the players get there, whatever they may be. The geography of this island can help me develop the history of it; by designing the geography of the place I’ll start to think about where settlements would spring up (if this island was ever settled before), find natural borders where conflicts might spring up, and things like that. Mapping the island – even an early map like this – isn’t necessarily the most optimal next step for me, but it feels right, and so I’m going to do it.

The first thing I did was put together some interesting shapes that contain the right amount of space, and printed them out.

Then I just sat and doodled island borders into them. Here’s what I ended up with:

Interestingly, as I moved away from drawing in 57 x 57 squares and began to draw in narrower spaces, I found that my instinct was to produce archipelagos rather than a single solid island. I think this might be the way to go about this project; one large ‘main’ island can comprise the bulk of the campaign, with other islands dotted around containing side quests and things of that nature (maybe… everything still needs to be explorable in 20 levels, remember). One of the benefits of having multiple islands is that I can scale the size of the setting up and down as I need it by simply adding or removing more islands, without having to re-design chunks of the main island.

That’s where I’m going to leave it this time. I want to draw some more island shapes and find something I like, while beginning to think about the kinds of terrain that might be here and the kind of history this place might have. At the beginning of this process I pulled out the notes from my old setting – the one that is sort of inspiring this one – and typed up everything that might potentially be of use to me. Next time we’ll look at what came out of that, and I’ll talk about any aspects of that old work that I think I might be able to reuse. And, with a little luck, we’ll start talking about the history of this place and what the players might expect to find here.