Every corner of this land is packed to the seams with dangers that would see you dead or worse than dead. Only difference between the Bitter Depths and all those other places is the dark. Down there you'll never see it coming.
The elves were the first to name the lands beneath Tairos. They called it Mal'hidun which, though difficult to translate to The Common Tongue roughly equates to: The Sadness that has Never Seen Light. Dwarven explorers would take little interest in the hollow darkness of this place. It ran too deep and demanded a tally in lives they were not willing to spend. So quickly was their decision made that they never bother name the place other than to refer to it as the Big, Blasted Hole in the West. It wasn't until Balmoran expeditionary teams began their brief effort to catalog the place that it took on the name most know it by. The Bitter Depths.
Balmoral's attempt at mapping the expanse was wrought with disasters, disappearances and death. The Haddich Expedition was the largest and most famous of all organized ventures into the Depths. It is from the few tattered journals and maps found by the Haddich Family's rescuer mission that anything concrete is known of the region.
From these scare fragments of information it is known that the Bitter Depths consists of a massive crater-like opening into the earth and the cave-system it leads to. The entrance area on the surface is known as the Black Periphery due to the charcoal colored earth that surrounds the crater and opening. The ground here is dead and nothing will take root in it. The entrance leads to a large chamber hundreds of meters in diameter and filled with smaller tunnels that splay out in various different directions and declines. Some are in fact just vertical drops as well suitable only expert climbers.
Many of these passages wind on seemingly without end only to terminate abruptly narrow impasses, underground lakes or empty voids. Some lead to veins of precious stone, exotic fungal patches and other such wonders but few have survived the trip to take in their beauty and returned alive.
The most well-known of the passages is the one that leads to the home of the Drekh , Sha'Hidun , the city that has never see light. While the tunnel itself has no clear demarcation one can look for hidden sigils or consult the maps made by the Melanthrin legionaries who oversaw the exile of their kin. That particular tunnel is a steep and difficult decline into the earth and marked by many dangers. Scattered reports place the distance from start to end at around fourteen to twenty miles and being rife with offshoot passages, false turns and massive open chambers.
Some scholars and explorers believe that the Bitter Depths is part of a greater network of cave systems that extends not just below Tairos but underneath the Endless Blue Ocean and perhaps to other distant lands if such a fantasy is even possible.
The terrain within the Bitter Depths is at best uneven and difficult to navigate. Most areas however are filled with debris, narrow passages, pit falls and flooded chambers. In some areas the temperatures range from extreme heat where geothermal vents break through the surface. In other areas the ambient temperature is just below freezing.
It is not without splendor though. Bio-luminescent lifeforms are plentiful and add a ghostly glow to the darkness. Shimmering crystals and diamonds made from eons of pressure and heat can be found here as well. Many of the cavern walls are pitted with glittering minerals that can make for a wonderful light show under the right circumstances. The water here is not just stagnant pools. Travelers will come across subterranean rivers and waterfalls crashing through glassy flats of ancient stone. Tiny micro-fractures and gaps leading to surface vents will often result in haunting winds that can whisper for eternity in the darkness of the Bitter Depths.
Fauna & Flora
Very little is known about the life that may populate the depths here. Only the closest tunnels have ever been explored and none of them recently. The few reliable notes come from the Haddich Expedition and they speak mostly of fungal life, simple cave-dwelling organisms and blind fish in the waters. The remaining notes mention some signs of primitive intelligence based on discovered cave drawings and simple tools but they do not know what made them. Only that the size of the drawings and the tools suggest something much larger than a humanoid was involved.
Stone, running water, fungal blooms and cave-dwelling animals