Greyhawk Underdark

From AJS.COM

The Underdark as in the wide-reaching civilization of Deurgar, Drow, Mind Flayers and other races ala Forgotten Realms, does not exist in Greyhawk per se. Instead, there are pockets of mostly unrelated civilization that span the underground world in everything from tiny mining colonies to huge dwarven fortresses and drow cities.

Contents 1 Why it is 2 What it is 3 Where it is 3.1 Jungle 3.2 Volcanic mountains 3.3 Terperate regions 4 Is thre more?

Why it is

The premise is fairly simple. In the real world, we are finding that giant cave complexes are often carved out of the stone of our world by bacteria, and only a very small fraction of these are still active. Most are deep networks of hollowed out rock, often filled with poisonous gasses, and rarely with major entrances from the world above.

In the World of Greyhawk, however, you have many intelligent and magical races that live underground. You also have a number of VERY large burrowing creatures.

All of this together would eventually lead to the purification (in terms of air) and population of these vast networks of caves, which in some cases will be connected by underground rivers or old tunnels made by large creatures.

What it is

So, I suggest that the Underdark of Greyhawk is not united enough to have a singular name. Some with call it Oerth Below. Some with call it the Underdark. There are probably dozens of names, and they're all equally correct, depdning on what part of it you're talking to.

As far as effects on the surface world, I would suggest that there are probably the most trading opportunities through the dwarves and gnomes who live underground, but interact with the surface.

Where it is

Jungle

We know that one large pocket of drow live under the Hellfurnaces. If we accept Shackled City's placement of Cauldron between the Hellfurnaces and the Amedio Jungle, then we can say that there is Underdark activity there as well, though, being so far south it may be unrelated, and could even be more directly tied to activity under the jungle than that under the Hellfurnaces. Jungle caves tend to be the most active in our world, and active typically means DANGEROUS. They will contain bubbles of active bacteria which produce sulphuric acid vapors, hydrogen sulfide vapors and simple carbon monoxide. Creatures that are immune to poison and/or acid would be the most likely denziens of such caves, making the various fungal creatures, black and green dragons and their spawn, kuo-toa, and the like not unexpected.

Volcanic mountains

In magma-created tunnels, caustic vapors will also be common, as would fire-loving creatures. Temperatures are likely to be high, even in places with no visible trace of magma, as volcanic activity typically means that magma will be closer to the surface. This would lead to a profusion of creatures associated with the elemental planes of fire and earth; red dragons and their spawn; fire giants; etc.

Terperate regions

In the temperate climates of the central Flanaess, I would expect extensive, but geologically dead caves which have existed for hundreds of thousands of years. These will include not just natural earth-dwelling creatures, but those denziens of the surface who tried of the sun and have escaped below. Undead such as vampires and liches are probably to be expected as well as living creatures such as drow, deurgar, gnomes, and other less humanoid creatures. The temperature will tend toward cool near the surface, and rise slowly as you descend. Temperatures a couple of miles down in old mines or deep natural cave complexes will easily reach the 40sC/100sF, and that is where you will start to find much less humanoid and much more fire/earth-oriented creatures.

Near the surface, you will likely also find a wide variety of mixed-environment creatures. Many kinds of nocturnal hunters such as bats, and many lycanthropes prefer to live underground, but hunt on the surface. These creatures may have a strong tie to those that live deeper. Either through trade when it comes to intelligent creatures, or as food/pets/protectors when it comes to the less intelligent.

Is thre more?

The 10,000pp question is: how extensive are these caves, caverns, rivers and the like, and how much do they connect? Is there some interaction between these clans, tribes, towns and cities of the "Underdark"? Do they have ties through above-ground civilizations? Are there planar portals deep in the earth that connect these various complexes to some demi-plane(s)?

There's quite a few possibilities.