Looking for Underdark hex mapping ideas and stuff

[Orius]

I'm looking for some ideas on mapping out my campaign world Underdark on a hex grid. The scales involved would be 1 hex = 1/5/25 miles. This is the same as the scale involved for the surface maps, but I'm not going to scale up to the 125 and 625 mile maps, since that's too big for Underdark maps IMO. And I'm not anticipating putting a lot of detail into the 1 hex = 25 miles map, that'll be to show where the main Underdark realms are located and trade routes between them, and stuff like that. The most practical scale for the Underdark would seem to be 1 and 5 mile hexes. I'm doing a tri-level Underdark -- an upper area that connects to the surface, a middle area below it, and a bottom area that extends far into the depths of the earth. I think the FR settng has a Underdark setup like this, but I'm not simply going to copy that world's assumptions.

I need some ideas on what to put in these maps, and maybe something like some random tables to generate new Underdark areas on the fly. Here's the stuff I'm going to do:

• Mushroom forests
• Large scale patches of luminescent moss/fungi
• Settlements/outposts for the main Underdark races (drow, duergar, illithids, svirfs, aboleth, kuo-toa, etc.)
• Subterranean lakes/seas
• Veins and ore deposits of stuff like mithril, adamantine, etc.
• Subterranean volcanic features
  

I'm not doing the old school Underdark magic radiation silliness that was behind drow gear degredation, teleporting difficulties, etc. I never liked that idea since it was just a way of screwing the players.

 

[grodog]

This info might be useful for you, Orius: http://melkot.com/locations/underdark/underdark.html includes both Maldin's underdark maps for Greyhawk, as well as a .pdf download version of the Dragonsfoot "Mapping the Depths of the Earth" project (now dubbed Encyclopedia Subterranica).

Other sources that might be useful for a large-scale drowic underworld include G3/D1-3, Night Below, A2/A4, Kingdom of the Ghouls (Dragon 70)/Empire of the Ghouls (Open Design project), and various FR books on drow, Menzoberranzan, etc.

 

[Orius]

This info might be useful for you, Orius: http://melkot.com/locations/underdark/underdark.html includes both Maldin's underdark maps for Greyhawk, as well as a .pdf download version of the Dragonsfoot "Mapping the Depths of the Earth" project (now dubbed Encyclopedia Subterranica).

First off, that index map is exactly the sort of thing I'm looking for. (And 1 hex = 1 mile too, one of the scales I'm using, yay!) So mapping at least in that example is more a matter of marking off which hexes have encounter areas and charting the paths between them.

Other sources that might be useful for a large-scale drowic underworld include G3/D1-3, Night Below, A2/A4, Kingdom of the Ghouls (Dragon 70)/Empire of the Ghouls (Open Design project), and various FR books on drow, Menzoberranzan, etc.

Most of that material I don't have unfortunately. I do however have Night Below, and in fact I'm going to start my Underdark maps with the areas from that module. I already have the surface areas converted to a hex grid and placed on my surface maps, and naturally linking up the Underdark areas accordingly seems like the best way to start things off. And that page does show some of the Night Below areas, albeit under the Flaness, but that's no big deal. I'll probably take a look at the Encyclopedia Subterranica if there's good stuff to rip o borrow for my campaign, I'm not really all that familiar with Greyhawk, but that pdf looks like it has some good encounters and stuff. I'll just need to convert it from 1e (oh hell, some guys wrote their encounters using 1e level titles rather than just listing levels). Anyway Greyhawk sometimes has more interesting stuff to yoink than FR.

 

[grodog]

This thread may also be useful, too: http://www.enworld.org/forum/showth...help-me-fill-in-my-2nd-Ed-Boxed-Sets-campaign

 

[Orius]

Yeah, I took a look at that thread the other day. I'm not a Greyhawk player, so there isn't much there for me to use or comment on.

 

[Razjah]

What about adding in ruins from places that fell from the surface during earthquakes or some cataclysmic event? They could then be take over by troglodytes aboleths, or some other creature.

A cavern with reflective crystals/minerals in the rock that appears to glow from a tiny little ray of light thousands of feet up being cast down and reflected everywhere.

Subterranean Design can have some cool pictures for inspiration. Like a giant chandelier made of bones.
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[Orius]

Some good ideas there.

Anyway, been doing some fact checking on this topic. I took a look over at the FR wiki and read up on the Underdark for that world. As I thought, the FR Underdark is divided into three sections: the Upperdark, Middledark, and Lowerdark. The Middledark is apparently supposed to be between 3 and 10 miles below the surface, with the Upperdark above it, and the Lowerdark below it.

However, I remembered that temperature slowly rises the deeper ones goes into the earth from pressure and heat radiated from within the earth's core. Doing some fact checking on Wikipedia, I found that the deepest point in the wrold with human activity is a gold mine in South Africa that goes down 2.4 miles, and the ambient temperature within is about 130 F (55 C). The idea that FR's Underdark is at least 4 times deeper than that is IMO patently ridiculous, just from how damn hot it would get down there. Then there's this sentence I found reading up about caves on Wikipedia:

It is estimated that the maximum depth of the cave cannot be more than 3,000 meters: deeper caves are crushed by the weight of overlying rock.

3,000m is about 10,000 feet, so I'll assume natural Underdark caverns don't extend much beyond that (making FR's Uberdark even more ridiculous). Of course that doesn't mean illithids, beholders, wizards, dwarves, and the like haven't delved deeper. But of course not too much deeper because of the heat. The link grodog listed above includes a page that has a cross-section of Greyhawk's Underdark that assumes a depth that only goes down 8000 feet (roughly a mile and a half) with most of the stuff less than a mile below the surface, which seems far more reasonable.

Still, given the heat deep within the earth, I think it might be interesting to have an extreme part of the deepest Underdark to take the heat into account. Below the deepest, darkest, areas of the Underdark where the illithids, aboleths, and even more frightening horrors that make the most cold-blooded drow assassins soil themseves with fear dwell, there are remote reaches of the Underdark which grow hellishly hot. In these areas, it's not uncommon to find extraplanar creatures such as fire elementals, salamanders, azer, efreet, thoqquas, heat-loving fiends and the like. There may even be portals and gates to relevant planes, like the Plane of Fire, the Plane of Magma, various fire and brimstone Lower Planes, etc. Also, for the evil DM, in an older edition of the game that uses infavision, all that ambient heat makes infravision utterly useless.

 

[Jhaelen]

3,000m is about 10,000 feet, so I'll assume natural Underdark caverns don't extend much beyond that (making FR's Uberdark even more ridiculous).
[...]
Still, given the heat deep within the earth, [...]

Well, why do you assume that the Oerth or Toril have exactly the same properties as planet Earth? Do they even have the same radius? Why shouldn't they have a colder or hotter core? And that's just assuming these fantasy settings represent a real planet in any way.
Take Glorantha for example: This world is flat. People live on an infinite plane and if you travel far enough up or down you end up in the divine realms. For D&D anything goes.

 

[Razjah]

Jhaelen's points are good ones. What about magic in the world? Or various cultures reinforcing the caves and creating vents or other methods of cooling the area? These could lead to having much larger and deeper cave systems.

 

[Orius]

Even if Oerth or Toril had dead cores, and the planet had cooled significantly (and thus less heat from geological activity, though there'd probably still be some from pressure), you'd still have to deal with all the weight that you'd get with 10,000 feet of rock. So unless the world has some kind of exotic subterranean stone with a very high compressive strength, it simply won't be able to hold up all that weight. Maybe a lower gravity world might affect things differently, but you can't drop the gravity too low or it starts to affect human physiology. I'm assuming the typical Earth-like planetary campaign world operates under the same physical laws that Earth itself does more or less. Natural, very strange and unusual worlds like flat earths might operate differently.

Note that I'm applying this to natural caverns specifically -- as I said above, Underdark races could have deeper tunnels that are reinforced by magic or superior engineering, and wizards are always violating the rules of nature. I don't want to have too much handwaved with magic either, after all the real world has some pretty damn interesting stuff underground.

Also, the Underdark is more three dimensional than what's going on on the surface of the world. An Underdark that goes down only a mile or two should give a DM plenty of space to work with, especially when you're taking into account how far things extend north, south, east, and west, as well as up and down.