The Alexandrian

Exit, Pursued by a Monster - Alex Drummond (Legends & Labyrinths)

An idea that I’ve toyed around with for years is creating a hex map for the Underdark. I still haven’t done it. But recently I’ve been running a huge technological complex for Numenera with a hex map that shares a lot of similarities with the Underdark. If the idea of running a hexcrawl through the Underdark is something you’d like to try,  I think there are a few key points to consider:

(1) What makes a hex map work is that it abstracts the actual terrain of the game world. If you’re doing a wilderness hexcrawl, you shouldn’t try to map every tree… or even every single country lane. If you do that, you’re defeating the entire point of the hex map. Similarly, if you’re designing your Underdark with a hex map you should not try to map every individual tunnel. (You might map major thoroughfares, the same way that major highways or rivers would be indicated on your wilderness hex map.)

(2) One key distinction between a wilderness hex map and an Underdark hex map is that, generally speaking, travel is always assumed to be possible through the side of a wilderness hex. This is not necessarily the case in the Underdark and one thing you’ll want to develop is a key indicating a minimum of three states for each side of the hex:

  • Open (there are lots of tunnels leading from this hex to that hex)
  • Closed (there are no tunnels leading from this hex to that hex)
  • Chokepoint (you can get from this hex to that hex, but only by passing through a specific keyed location)

Note that the existence of a given chokepoint could also be a secret that needs to be discovered (by either obtaining the information elsewhere or perhaps by performing a detailed survey of the area).

(3) The RPG industry has developed a fairly standard “vocabulary” of wilderness terrain types. (These actually predate D&D and were inherited from Avalon Hill’s Outdoor Survival when Arneson used it as a template.) These terrain types also have the benefit of being familiar to us in our every day lives: We know what forests are. We know what mountains are. And so forth. IMO, you’re going to want to develop a similarly interesting vocabulary of at least 4-5 different Underdark terrain types. And you’re going to have to figure out how to clearly communicate those differences to a group that probably doesn’t contain spelunkers (and certainly no fantasy spelunkers). The point of this, obviously, is to make the map more interesting: This both rewards exploration (a key component of any hexcrawl), but also to make the actual description of the PCs’ journey more engaging.

(4) The Underdark is fundamentally three dimensional in a way that the surface of the world is not. Keep that in mind, but don’t worry about it too much: The surface of our planet varies from 1,400 feet below sea level to 29,000 feet above sea level but we still successfully visualize it as a flat plane. Consider the minor elevation shifts I discussed in Jaquaying the Dungeon and apply the same logic at a macro-scale here: You can probably make your Underdark more interesting by saying “you have to go down and then over and then up to get to there”, but vast slopes and slants and descents and climbs can be abstracted onto a two-dimensional map. So go back to Point #1 above and remember to embrace the abstraction of the hex!


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9 Responses to “Thought of the Day – Hexcrawl in the Underdark”

  1. Brotherwilli says:

    Have you hit upon any Numenera-specific ideas when it comes to a hex-crawl? I’ve been using your earlier articles to put together a small one to introduce a new group to the game; Numenera seems to take to a hex-crawl marvelously due to its focus on exploration and easy justification for unusual discoveries. Are there any game-specific recommendations you have?

  2. Wyvern says:

    If and when you follow through on this idea, I’d be very interested to know what terrain types you come up with for the Underdark.

  3. Rorschachhamster says:

    Well, thank you. Now I’ll have to do a lot of brushes for Hex-GIMP… it’s not like I have other things to do… 😉

  4. Kinak says:

    Well, let’s see…

    Limestone Caverns – I feel like these are a basic terrain type. Lots of stalactites and stalagmites, narrow tunnels, and underground rivers.

    Volcanic – Lava tubes, hot springs, and sulfur are the order of the day.

    Fungus Forest – You kind of need to have this one. It’s unrealistic, but I don’t think anyone has trouble understanding it.

    Underground Sea – A large cavern or series of smaller caverns filled with water. May have breathable air above the water in some areas.

    Vault – Much of the hex is one huge open area. Easy to move around the floor of the vault, but potentially a problem moving at higher levels and not a great place to use light sources.

    Burrows – Open space in the hex is mostly dug out by a burrowing creature. Probably fairly easy to move through, if you know the way, but high likelihood of encounters.

    There are probably some more fantastical options too, but those feel like a good start.


  5. S'mon says:

    I tend to use the Lands of Deepearth map from the old 1e AD&D Dungeoneer’s Survival Guide as my inspiration for successful Underdark 3D mapping. Map doesn’t seem to be online, though.

  6. Jason says:

    During 4th Edition, I ran an Underdark hex-crawl. I had certain large terrain features mapped out (like a massive, jagged chasm that split my map in two with only one hex of bridge across it, or a long route south to get around it). But my favorite thing about it was to make navigation unpredictable.

    Each hex border had a number; that was the DC for the dungeoneering check to successfully navigate the passages. Many of them were low or middling difficulty, but a few were higher (to represent especially labyrinthine tunnels, or challenging navigation). If the PCs failed the check, I would roll a d6 to determine where they ended up instead. This only happened two or three times through the hex crawl, but it really drove home the confusion of trying to find a path through an endless maze of tunnels.

  7. rabbiteconomist says:

    I am running a Underdark hexcrawl right now for a pathfinder homebrew. I got inspiration for the idea from this post months ago. The group is enjoying their first hex crawl.

    It is interesting to note that the exploration rules offer no advice for underground exploration. Their product Into the Darklands from 3.5e does provide some good ideas for dead ends, verticality of tunnels, tunnel widths, and survival checks to find safe camps. I found this resource after stocking my hexes. I settled on 3 days of exploration per cave hex excluding exploring hostile dungeons – only mountains have the same verticality a cave of the main terrain types.

  8. Dan Dare says:

    Just came on this and I am preparing to make just such an underdark map. My thought is to allow 3 levels of depth. In each hex I can indicate each of the 3 levels if they are present with connections to other hexes but also up and down. Each of the 3 levels will probably only be present in about half the hexes for that level, so 50 per level for 150 total, compared to 100 in the surface campaign above. That should be enough to make it seem very rich and complex. Then there is a question about egress to and from the surface. I’m thinking of limiting that to about 10 hex locations.

    Kinak @4 : cool.

    Also what about some more water features? A river runs through it, a lake, an whirlpool taking you one way to lower levels, a water spout taking you up?

    Some fantastical areas like the daylight chrystal caverns or the teleport vortex where you just don’t know if you are going left or right, up or down and how far are you now from the hex edge?

    Atmosphere effects like the vacuum chambers, methane crags, fog corridors.

    Jules Verne had some cool ideas in Journey to the Center of the Earth.

    And civilisation structures – city hexes, mines, great highway roads complete with tall bridges, maybe abandoned and broken?

  9. robin says:

    “Terrain” might be more usefully why the cavity exists. Eroded cave, lava tube, (monster) burrow, (race) mine/quarry, (race) city; race = dwarf, drow, goblin, etc; monster = worm, beholder, etc.

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