Walk quietly and douse your lights. There are things here that can see through solid stone and feel your ragged breath as you take it. None of them are friendly, all of them are hungry.The true depth of the Underdark is unknown and most assume that it extends to the true bottom of the world where the fabled Abyss Ocean hides the atrocities that the god Caspian drove from the upper seas. Because of this, there are waterways and dark seas that exist far beneath the surface but their true depth is unknown and it is impossible to say where they connect to the vast oceans of Isekai without diving in and charting the paths through experience. For the adventurer that wants to find new or forgotten paths, they might think that the Underdark is a grand place of opportunity but the reality is that it is a graveyard for the inexperienced. Paths can suddenly shift and collapse, the routes between Underdark provinces can collapse from natural occurrences and ancient creatures that were chased deep underground by the Huntress search for their chance at an easy meal or a way back to the surface. The underground paths and caverns experience no change in seasons, the day is not known from the night and there are few sources of light that occur naturally. The gems or plants that can create their own sources of light are highly coveted and communities often form around them while the creatures that can produce their own light find that it makes an effective lure for the sake of hunting adventures. Concepts of time change for creatures that live below ground, some have adapted to measure time by the formation of crystals or the life cycle of fungus while others have lost touch with that aspect of reality and sleep only an hour or less for each day on the surface. While the dangers of the Underdark are many, the soundness of one's mind is a forgotten danger to many, for those that lose their way in the winding, endless caverns may eventually forget the color of the sky or the warmth of the sun as their mind gradually begins to lose touch with the world that they once knew. Those that seek to retain their sanity bind themselves together in grand cities or interconnected kingdoms. The grand mines and halls of the Dwarves reach only so far into the Underdark while the dwelling places of the Duergar and Drow can be found unimaginably far below the surface. These often exist as stand-alone organizations where the more civilized Underdark denizens will trade, rest and fight for their territory while the zealous will crusade farther into the depths in search of ancient evils to exterminate. There are also Dragons that seek out the concealment offered by the Underdark and hide their great treasure hoards deep underground, their presence is often considered to be fearsome and terrible to the point that even a Metallic Dragon that lives deep underground is not considered an ally if you trespass into their caverns. Since the Eldritch War, there has also been an increased presence of otherworldly creatures and unspeakable horrors that do not originate from Isekai that have many eyes, limbs, bodies that do not appear to obey the natural laws and physics established in knowledge and some of them wield fearsome psychic abilities. With these dangers, there is a sense of dread and misfortune that hangs about the Underdark and is generally understood in any culture that has a known Underdark path whether temporary or established. However, there are many things that would tempt adventures to venture here aside from exploration and glory. Precious metals, jewels the size of which would cause a Dragon to covet your wealth, relics of ancient empires and earlier ages when the gods walked freely among mortals. Many of the secrets of the world are locked away in the Underdark, a place that while in constant motion has an uncanny knack for preserving and remembering things that the Dragons do not know and that the Sphinxes will not talk of. It has been said that a civilization of the Ancient Fey once existed that had gained complete knowledge, that understood the entirety of the world and the expanses of all the tunnels and oceans within it. This civilization journeyed to the very bottom of the world and took with them magic and knowledge and secrets that were wiped from history for reasons that are unknown even in legend.
Quick Facts: Geography
Lowest Point: Unknown
Highest Point: Located in the "Metallic Council"
Subterranean Oceans: 13 large oceans known
Fresh Water: Plentiful and High Quality
Illumination: Dim to Pitch Black
Average Temperature: 65 Degrees
Average Tunnel Clearance: 5-10 feet tall
Average Tunnel Width: 2-7 feet wide
Average Tunnel Visibility: 10 feet ahead
Sound plays many tricks on those that are unused to the darkness.Those places that have natural light are dimly lit, either by some stray ray of light that has found its way through reflections into the darkness or due to any of several types of luminous plants in the area. There are a few crystals and metals that can also produce light if the proper conditions have been met, often these are found in Underdark cities providing a dim red, blue or gray light that allows the citizens to see with relative ease. The general rule for light is that the deeper you go, the more rare plant-produced light will become which forces you to rely on finding crystals or mystical metals but lights that move deep in the Underdark usually signify a predator or animal that has the ability of bioluminescence. Whether by natural chemistry or magic there are many creatures that use light as a means to lure others to specific areas, none of these creatures have good intentions. For those that have highly developed Dark Vision, the Underdark is a mysterious world full of beauty and danger that houses incredible rock formation, giant cliffs, waterfalls and views that cannot be found on the surface world but most travelers will never notice such things as they cower in fear from the darkness.