Tropical Island Generator for Fantasy TTRPGs
Z Wilson
Introduction
The purpose of this tool is to help a worldbuilder develop an island or archipelago for use in a fantasy TTRPG setting. It is best to think of these procedures and guidelines as a more structured way to go about the top-down creation of a setting, a method I enjoy despite being fairly labor-intensive. I'd like to think that this tool lends itself to "fractal" world building, world building that starts vague and zoomed out but gains detail and complexity as you focus on specific parts. Some of the creative labor of deciding what to put in a given place has been put off to random chance in order to save more energy for other parts of developing an adventure setting. It is also important to note that this tool is meant to create an entire island with at least two dozen specific adventure locations, not the adventure locations themselves. The end product should be two maps, one more abstract than the other, with around 25 locations of varying purpose.
This tool assumes the existence of one or more ancient civilizations in your setting that have since collapsed and left behind ruins, some kind of intelligent, native entities that threaten those who leave protected settlements, and some sort of subterranean megadungeon that sits underneath each island or archipelago. While this tool has been written with fantasy tropical islands in mind, it should not be difficult to change things to better suit whatever kind of setting you prefer. The principle of “put a bunch of stuff on a grid, draw a map around it” will hold regardless of specific setting. Just be aware that the table for determining what is at a coordinate is a 2d6 table, meaning mid-range numbers will be rolled more often than high and low numbers.
Consider the steps in this procedure as suggestions more so than hard and fast rules. The whole point of this is to help spur creativity, so if going against these guidelines results in a more interesting setting, do it. This is just one way to develop an area with interesting locations and things to do, and it probably will not work for everyone, but hopefully someone will find it useful.
Procedure
Step 1: Make a 10x8 grid in either hexes or squares. Orientation is up to personal preference, but all of the examples I make will be landscape orientation. Make sure that the sides of the grid are numbered such that the longer side is numbered 1 through 10 and the short side is numbered 1 through 8 in order to create a coordinate grid.
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| This is a scan from my notebook, showing how I like to start my maps. |
Step 2: Fill out the grid. Roll 2d4 and add 20 to the result, this is the total number of points of interest that will be on your map. Now roll a d8 and a d10 together. Use the numbers on the d8 and d10 as coordinates on the 8-long and 10-long sides of the grid respectively. This will determine the location of the point on the map. For each point, also roll 2d6 on the following table to determine what is located at that point (see the “Location Traits” section below for location inspiration). If there is already a point of interest at the rolled coordinates, either place the new point nearby, or keep rolling coordinates until a new point is rolled. Feel free to add more points of interest of any type during any step, particularly if you feel like there need to be more of any specific type of location. It is often good to have at least one town, city, fort, or otherwise friendly location for player characters to start in, but it may be more exciting to drop the party off on a completely unexplored island as well.
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| Here are the random locations I rolled for an example island. It kind of forms a ring with R8 in the center, and I think I can do something interesting with that. |
Step 3: Draw the outline(s) of the island(s) for a “geographic” map such that all or most of the points of interest are on land. Add mountains, volcanoes, forests, swamps, deserts, etc. as you see fit. Now is also the time to add roads, trade routes, or lines of communication between points of interest, if at all appropriate. It is at this point that one should start creating a more abstract “web” map of the area where points of interest are represented by points on the web. Points that can be easily reached without going through other points are connected to each other by lines. In this “web” map, a line should represent an unbroken, well-known route between two places with no other major locations between points A and B.
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| Aaaaaaaaaaaaaand draw the rest of the damn owl. As far as instructions go, I started with the outlines and then added mountains and forests after. It may be difficult to just create an island around some random points, but that is why I wanted to try this method in the first place. |
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| Something like this is what I mean by a web map. Megadungeon entrances are connected via subterranean tunnels so while they technically have direct routes between each other, they constitute very dangerous journeys for the ill-prepared. |
Step 4: Determine a geographic area by looking at your “geographic” map and finding contiguous areas that share a common climate, geographic feature, or plant community that distinguishes the area from others on your “geographic” map. With this process in mind, it should be possible to view your “geographic” map as a continuous patchwork of different geographic areas. It may be useful to somehow note which points of interest are inside which geographic areas on the “web” map, although the same result could come from a traditional list as well.
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| This is the much messier version of the web map that I would actually use when running the Dragon's Maw, for better or worse. |
Step 5: Either pick a town to start with or start with the only town on the map and give it a name. Detail the town to a point where you could comfortably run the start of a session in it and then start detailing the nearest points of interest and geographic areas. Essentially, start with one point and radiate outward so that the most detail is present closest to the chosen starting point. Do not worry about giving detail to every location prior to the first session on the island unless you want to, a name for each location and 2 or 3 of them detailed enough to run an adventure in
ought to be enough.
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| The descriptions of the two smaller towns of the Dragon's Maw. At this point all I would want to be able to run either in a game would be a list of notable locations and the important people at each location, but I could probably run something passable with just these descriptions and improv as well. |
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| This is the description for the third and largest town I detailed for the Dragon's Maw. While it is a large town, it is not quite a city so I do not have the opportunity to detail a city in this example. For what it's worth, I do not detail cities much differently from towns, and I will be posting several example islands with cities on them in the future. |
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| This next series of images is of the spreadsheet I made to keep track of all of the locations I made for the Dragon's Maw. All of this will be available as text and not images in a later post as well. |
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| The encounter tables for each of different zones of the Dragon's Maw. I probably should've made one for the tunnels connecting the megadungeon entrances, but I prefer to run that travel differently from how I would run travel between the other locations, so I decided against it. |
Step 6: Begin thinking about the history of the island. Due to the random nature of this method of creating islands and filling them with locations, some things might be located in strange places compared to what one might expect from the real world. Start with the explanations for why those things are located where they are when you detail the histories of these places. Things in the real world are not always in the most optimal location, but there is usually a good reason for this as well. It may be useful to note that the implied fantasy setting of this generator puts magic on the table as an explanation for nearly anything that doesn’t make much sense, but be conscientious of how often magic gets used as an excuse.
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| This is what I was able to come up with for the Dragon's Maw. This level of detail for the history is hardly necessary, but I enjoy thinking about it. |
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| This is is probably the most important section to write for an island's history because the recent events are what will inform the problems to solve and adventures to go on in many cases. |
Location Traits
While Step 2 of the procedure provides a table of location types, this section is meant to provide a random table of traits for each location type. These will be single-sentence descriptors that can be a starting point for a more detailed description. It may be useful to roll two traits for locations and use any conflict between the two traits as inspiration for adventures. The tables in this section are 1d6 tables.
Table D: Dragon’s Hoard
Table O: Otherworldly Incursion
Table U: Unique Creature’s Lair
Table B: Basic Creature’s Lair
Table N: Native Intelligent Entity Settlement
Table R: Ruins
Table M: Megadungeon Entrance
Table T: Town
Table F: Fort
Table W: Wizard’s Tower
Table C: City
A Few Notes on Island Ecology
Full disclosure: I have a degree in conservation biology, a field which tends to be more focused on entire populations of organisms and how they interact with humans and the environment. As a result of this education, I happen to know enough about ecology to make this section very long indeed. I will, however, attempt to keep it relatively brief.
There are many things that one should consider when trying to describe any ecosystem, but when developing fictional settings I find it helpful to start with where the heat and water that allow life to take hold in an area are coming from. The heat in most ecosystems on Earth comes from the Sun of course, but there are also ecosystems such as those around hydrothermal vents on the ocean floor where the heat comes from the vent itself. Water can be easy or difficult to source depending on the organism in question, as some organisms are adapted for salty water while others are adapted for fresh water. Species that can safely drink salty water often cannot survive in an environment where there is only fresh water. Organisms that need fresh water to survive, such as humans, are often reliant on rain to supply them on islands, as that may be the only thing adding fresh water to the water table of the island.
From there, it helps to decide what direction the prevailing winds near the island travel in. It is probably best to arbitrarily pick a direction unless you know enough about where the island is located on the world map of your setting to take a swing at global wind patterns. All that is really relevant to making islands is that the direction of the prevailing winds will determine the windward and leeward sides of the island. The windward side of the island will be the side that the wind runs into and the leeward will be the side where the wind returns to the water. In general, rain clouds will move with the prevailing winds, causing the windward side to get the most rain and be the most hospitable to plant life. The leeward side will tend to get less rain, particularly on islands with large mountains or mountain ranges that create a rain shadow, an area on the leeward side of a mountain which gets less rain than the windward side. This does not mean that there are never lush forests on the leeward sides of islands or that the windward sides are always covered in dense plant life, however. The thing that determines what kind of plant community you find on a given part of an island is how much water is available, not the wind.
With a base in heat, wind, and water, it is important to know how living things get to islands. When an island first emerges from the water, there is no visible life on it. It is possible that life will never arrive on a given island and it will be barren until it is swallowed back up by the ocean. Even if living things make it to the island, they must also be able to survive long enough to reproduce and establish a growing population, something which is not guaranteed either. In the case of a totally barren island, birds are able to fly to them and may use them as nesting sites to avoid terrestrial predators, since many seabirds get their food from the ocean and not the island they nest on. Some plants are already adapted to colonizing new land and may not require soil or even a sandy beach to take root, anchoring themselves to bare rock if need be. These plants often have some method of sending their seeds far away, via air or water, in the hopes that the seeds will land on something solid for long enough to grow and produce their own seeds. This will create soil because over the course of millions of years, plants can convert even a mountain of bare rock into fertile soil that will support plants and animals that could not have survived on the island when it was brand new.
These more mature islands that have soils and established plant communities are much easier to get a start on, so organisms do not need to be as specialized to be able to colonize them. Plants that can send their seeds far afield but can’t grow on bare rock will be able to colonize these more mature islands. Once plant communities are present, it is also more likely that an animal that does not normally get its food from the ocean will be able to survive if it somehow gets there. There have been cases of animals reaching new islands because they end up on a piece of driftwood that travels across the ocean to some random island. This “rafting” method of island colonization is known to have happened several times in Earth’s history and accounts for many of the non-avian vertebrates present on real islands. While these colonization events are relatively rare on the scale of days or months, it can happen many times on a given island over the course of millions of years. The things that do establish themselves can go on to evolve into several different species that take advantage of different resources because of the lack of competition on the island.
The final concept I would like to cover in this section is a basic principle of island ecology, the idea that larger islands that are closer to land tend to have more variety in species than smaller islands that are farther from land. Size is important because islands are colonized by wild plants and animals essentially at random and a larger island is more likely to get in the way of a coconut floating in the ocean than a smaller island. The distance from the mainland is also important because the mainland is frequently the source of the species that colonize islands. This can be muddied when you account for other islands in the area also producing organisms that could be swept out to sea on a log or something, but the important part is that being closer to the source of colonists means it is more likely those colonists will be alive if and when they reach the island.
To boil all of this down into a few sentences, I recommend thinking about the ecosystem of your island first in terms of where livable temperatures and usable water come from, followed by the general patterns of the wind in the area. These three things together give a big picture view of what types of plants you can expect to find on different parts of a given island. Newer islands with fewer plants can only be colonized by species that are either very tough or do not rely on the island for food and water, while more developed islands with lots of plants might not even seem that different from the mainland. Larger islands that are closer to the mainland will tend to have more species diversity than smaller islands farther from the mainland, and evolution doesn’t pause on islands, so don’t think that colonization is the only source of new species on islands. Hopefully this was a useful insight into how the ecosystems of islands form and grow over time, but it was by no means comprehensive, so feel free to do your own research into island ecosystems.
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