The following are the Realms beneath the surface of the world. Quite often these exist without the inhabitants above knowing anything about them.
This is a name given to represent the caverns deep under the Wyrmspine Mountains. These jagged, twisting tunnels have mostly been explored by dwarves and many tunnels have been worked or are intersected by abandoned mine shafts. Whilst earth dwarves dwell in the fringes, Arzun Kluthek is mostly beneath even their realm, and is home to many stone dwarf holds. Whilst most mine the earth out of greed some also do so out of insanity with the intent on releasing the Dark God from its prison. The region known as Arzun Kluthek stretches far to the north and south of the central Wyrmspine Mountains and the tunnels join with those of Deep Danatha to the west. There are reputedly tunnels that stretch eastward, under the Endless Prairies and connecting to the Chasm of the Crescent Moon.
Usually referred to as Brokkenbaal the Bleak, this Homeland is the Underdark of central Cardan lying deep beneath the Westernwall/Dividing Mountains. Its primary residents are stone dwarves with more deep orcs in the southern regions where the caverns border upon those of Ruk Grulath. The caverns of Brokkenbaal are mostly narrow, twisting affairs, widened in places by the stone dwarves whose mines and holds occupy many important junctures and caverns. The stone is predominantly a dark, pitted rock, which crumbles easily and shelters vast coal deposits. This blackness seems to sap any light brought to the realm and even has a muffling effect on sounds.
Located beneath the frontier, these sprawling caverns of blackness stretch from the caverns beneath the Wyrmspine Mountains (Arzun Kluthek) to the sea. Commonly referred to by the surface races as simply the Night Below, the realm is mostly the home of the dark elves that were banished here thousands of years ago. Black elves wander in and out of this area of the Underdark and stone dwarves are numerous in the east. Troglodytes make their homes far away from the drowathir’rin cities and kuo toa are frequent visitors from the depths of Mirdeth and their realm of Yoodulrudoop where the caverns meet the sea.
The caverns of Deep Danatha are vast, mostly large tunnels, many of which still have waterways that empty into Mirdeth. Other, dry caverns serve as extensive trade routes and secret ways for dark elves to use when raiding their surface kin. Drowathir’rin cities are set up at most important junctures and in the largest series of open caverns.
LOST TUNNELS, THE
Practically unknown to the inhabitants above in the Heartlands, this realm below has for many generations served as a battle ground between the stone dwarves of Brokkenbaal and the deep orcs of Ruk Grulath. Recently more sinister and powerful creatures with slimy skin and tentacled faces using strange magics have taken over and enslaved any trespassers in their domain. It is unknown where these ‘mind flayers’ came from. Some speculate from realms even deeper than the Lost Tunnels and others from a distant plane. The increased presence of fiendish creatures in the tunnels may support the latter, though it’s possible they are the result of taint from below too.
The tunnels themselves are far-reaching and generally wide and rounded making travel easy. However some are water filled and few have any connections to the surface world. They are referred to as the Lost Tunnels because in early history the Brymori humans found them and explored them, but during the reign of the Exalted Kingdom all known entrances into the underdark were plugged and destroyed.
Mirdeth or the Nightmare Waters refers to the deep caverns that lie even beneath another Underdark realm, Deep Danatha. The waterways and vast black lakes of Mirdeth are found in large pockets all along what is the Frontier on the surface. Water flows through the caverns of Deep Danatha and in a series of cisterns and steep cascades makes its way down to the vast underground lakes of Mirdeth. Even the drowarthir’rin that live in the caverns above rarely venture into the deep Nightmare Waters. This is a realm of strange oozes, bizarre aquatic creatures and the home of many kuo toa. There is also believed to be at least one portal to the Abyss somewhere in this night below.
Ruk Grulath is a vast orc realm deep beneath the Sanctuary Mountains of Cardan. The northwestern tunnels connect with the tunnels of Brokkenbaal, home of the stone dwarves and the south tunnels stretch far beneath the lands of Carantha. It was in these tunnels that a vast magical realm was established by orcs of a long-gone era. The deep savages who dwell there now have little knowledge of this time or of the artifacts and ruins they stumble upon in the caves, though, strangely there are still a larger number of sorcerers amongst these orcs than other orc populations.
Like the caverns to the north the stone here is black and pitted, but it is of a harder nature. What really make this Homeland unique are the vast chasms that split the caverns here. These ruptures, many caused by the Invoked Devastation, also lead to the name given to this realm by surface races; The Yawning Abyss.
Yenzari refers the extensive underdark tunnels that stretch beneath the Basalt (Fireplace) Mountains. More recently they have become known as the Smoking Pits as severe volcanic activity in the north has collapsed or otherwise ruined much of the tunnels. This has forced many obsidian dwarves to the surface. Whilst the cannibalistic dwarves try to make their way on the surface their enemies, the giants, are taking more and more territory in Yenzari as they adapt to the hot environs. Other fire creatures are found here including azer who were considered gifts of the ancestors by the dwarves.
Yoodulrudoop is essentially the far western caverns of Deep Danatha, where the vast tunnels meet the sea. All along the coast of the frontier water-filled, underdark caverns are teeming with kuo toa, with some kapoacinth, merrow and sahuagin in the south. The presence of aquatic elves have kept numbers of the evil underwater dwellers rare in the far north, but from about a third of the way down the frontier evil reigns. Beneath the tropical waters of the far south sahuagin dominate, refusing to even cooperate with the other evil denizens of Yoodulrudoop. These caverns are named after the huge kou toan realm just south of the aquatic elves (just south of Larefian forest on the surface).