Developing an Old School Sandbox for 5E – Part 3

I’ve posted a couple of times about developing a sandbox setting for D&D 5E (Part 1, Part 2), and this week I’m going to expand on the climates, terrain, and monster selection.


As my sandbox is an island, and it’s not so large as to be a full continent, there is a limit to the different climates that I can realistically include. I’ve decided that this island sits in the northern waters of the world, and so climate reflects this.

The island itself is slightly larger than the Northwest Territories in Canada—the surface area is approximately 916,249 square miles (1,474,560 square kilometers). So this gives me some room to work with.

Using the Köppen climate classification types to describe the island, the southern and middle portions of the island are subarctic climate, the northern portion of the island is polar tundra, and the higher elevations are dry-summer subarctic.



This has a direct influence on both the terrain types I will use and the monsters I plan to include.

Terrain Types

As mentioned previously, the 5E DMG provides lists of the monsters divided by terrain type. The terrain types listed in the DMG are Arctic, Coastal, Desert, Forest, Grassland, Hills, Mountains, Swamp, Underdark, Underwater, and Urban.

So applying these terrain types to the island based on the climate I’ve chosen, I get the following:

  • Arctic—The mountains in the northeast of the island use the arctic terrain type. This is due to their elevation in addition to their latitude, increasing the sub-arctic climate to arctic as you climb higher into the range.
  • Coastal—As this is an island, the coastal terrain type is definitely applicable.
  • Desert—Even though the mountains provide a rain shadow for the interior of the island, I don’t want it to be too dry. A sandy desert is out, and I don’t feel the island is far enough north to get a dry snow desert. So I’m not going to use this terrain type on the island.
  • Forest—Most of the middle and southern portions of the island are subarctic and therefore forests are very appropriate. The forests are almost exclusively conifers (needles instead of broad leaves) which remain green throughout the cold months. It’s not unknown for the occasional broadleaf forest to be found within a subarctic zone, and so I’ll probably include one in the southern area of the island.
  • Grassland—The northern tundra can be considered a grassland for the purposes of monster selection by terrain type, though the vegetation is very short and is composed mostly of shrubs, mosses, and lichens. The central area of the island is also covered by a grassland.
  • Hills—Each of the three sets of mountain peaks are surrounded by foothills. In addition, one of the sets of hills extends out into the central part of the island (near the grassland noted above).
  • Mountains—As mentioned, there are three distinct sets of mountain peaks. The mountains in the northeast are fairly low and very cold. The mountains in the southeast are essentially a continuation of that same chain, though the ground between them is low enough that they seem as if they are a separate set of peaks. The mountains on the west side are much larger (cover more area) and have a higher elevation.
  • Swamp—The tundra in the north transforms into swampland during the short summers when the temperatures rise enough to thaw the ground frost. The ice melts and creates many bogs and marshes (as well as lakes and streams).
  • Underdark—This is less a “terrain” type than it is a location that can underlie almost any of the other terrains. On this island, the underdark will be mostly found underneath the hills and mountains. As I plan to have this campaign be mostly about exploration of the island itself, I’m not going to make the underdark too extensive.
  • Underwater—Like the underdark, I don’t want to run an extensive underwater campaign. Therefore, I plan to have a large lake with underwater ruins that can be explored if the PCs are interested, but it won’t be a major part of the campaign.
  • Urban—The point of this campaign is a wilderness hexcrawl focused on exploration. So I’m placing a small town that is the PCs starting point, though I don’t plan to put any adventure hooks that lead to purely urban adventures there. I also have ideas for two other small settlements on the island, but they won’t be sizable urban environments. The one possible exception to this is that there are the ruins of a small city on the island that is entirely abandoned by people after some kind of disaster, and only monsters can be found there (as well as some interesting mysteries and cool set pieces).


So I have my climate, and this affects the terrain types to include on the island. And now I have to select my monsters.

  • Humanoids—The first choice I need to make is about how many humanoid races I want to include. D&D contains many different options here, such as the goblin races, orcs, drow, bullywugs, derro, duergar, firenewts, gnolls, grimlocks, grungs, kenku, kobolds, kuo-toa, lizardfolk, merfolk, sahuagin, tabaxi, troglodytes, and yuan-ti.

    Obviously, including all of these would be far too much. Some I can eliminate simply by climate and terrain type (such as yuan-ti), and others just don’t really fit into the setting (grungs).

    Still, that leaves me with many options.

    For now, I expect that I’ll include some form of goblinoid race (probably straight goblins and perhaps bugbears, but likely not hobgoblins). I may also include orcs as a tribal race that inhabits the tundra in the north. As far as the bits that take place in the underdark, I will likely include duergar and one other—most likely either grimlocks or troglodytes, whichever I can make the most interesting.

Of the other monster types, these will be selected on a case-by-case basis:

  • Aberrations—I will definitely include a few aberrations with each as the core monster for a larger encounter area. My plan is to create a few new aberrations to provide something new for the PCs to discover.
  • Beasts—Natural animals will certainly populate most of the wilderness areas, and I will also include some of the giant versions and a few of the larger beasts. Dinosaurs will not be found on the island.
  • Celestials—As celestials are native to the Upper Planes, and generally are of the same (or similar) alignments to the PCs, I don’t have plans to include these creatures (unless as a one-off for a particular encounter area).
  • Constructs—I will certainly include a few constructs on the island, mostly as remnants created by those who lived in the ruined city on the island.
  • Dragons—I do have plans to include at least one dragon, as I have a new race of creatures related to dragons that will play a part in the setting.
  • Elementals—These creatures will appear as appropriate to specific encounter locations only.
  • Fey—Some types of fey will certainly inhabit some of the wild places on the island, though they certainly won’t be common.
  • Fiends—Like elementals, these creatures will appear as appropriate to specific encounter locations only. I do have a couple of ideas already, so there will definitely be a few included.
  • Giants—I do plan for there to be a couple of types of giants on the island. I do not intend to use the Ordning or anything similar to constrain the giants into a hierarchy.
  • Monstrosities—I will certainly include some monstrosities in my list of monsters on the island. They will most often be part of specific encounter locations, but some can be found in the random tables.
  • Oozes—These will be included as appropriate to the climate and terrain type.
  • Plants—I do plan for there to be some plant creatures on the island, and I intend to create a few new ones for PCs to discover.
  • Undead—There will certainly be undead on the island, though they will not be a focus of the campaign.

Island Regions

Now I’m in the process of creating specific regions on the island. A region can be as small as one hex, or as large as I need it to be. A particular forest will usually be a single region, and a region could include an entire mountain range or just a single mountain, depending on its relationship to the surrounding terrain.

From the moment the PCs leave the main town, they will move from one region to another as they explore the island. Each region will usually have a noticeable boundary (such as the edge of a forest into a grassland, or crossing a river into a new area), though some may have large transition areas as regions overlap for some miles.

In some cases, the regions may be defined by the monsters themselves. For example, if I choose to include a colony of ettercaps, they may take over part of a larger forest. While the forest itself could be a single region, it would generally make more sense for the spider-infested area to be a single region, with the regular portion of the forest a neighboring region.

For this reason, the development of regions and the placing of monsters basically goes hand-in-hand.

Random Encounters and Set Pieces

And, of course, once the regions are developed, each one will get its own set of random encounter tables, reflecting the creatures that could be found in that particular region.

Each region will also have at one set piece encounter, and probably a few. These are locations that do not change and are not random. For example, a goblin lair where a particular goblin tribe lives would be a set piece encounter, with a map of the lair and description of the tribe and its members.

Not all set piece encounters will necessarily include monsters, of course. When exploring a hex, there will be interesting things to find that won’t always lead to a fight, or even interaction with living (or undead) creatures.

But this the final, and longest, step in developing the sandbox and will take some time to do.


I’ve been picking away at this setting here and there as I work on other projects, so it’s not moving terribly quickly. I hope, though, that my thoughts here provide some insight into the development of such a sandbox setting.

I’ve already started planning out the regions and marking them on the island map, and I’ve created a couple of the hexes in the first region. The next time I update this project here I will include some of the developed regions and a couple of completed hexes so you can see how I will present the information for use when running the game.

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