Draconis is a world of darkness. It is a planet with functionally no surface, as the rocky center is surrounded by an atmosphere of caustic aerosolized acid, heated to over 800 degrees Fahrenheit, much like the atmosphere of Venus. Only creatures immune to Acid, Fire, and Poison damage are able to thrive on the surface, and as those attributes rarely exist in peaceful creatures, they generally starve to death before gaining a strong foothold.
The true action of Draconis is all subterranean, in the massive labyrinthine cave system that pervades the entirety of the planet. Caverns are rarely, if ever, more than 60 feet wide. These caves are caused by erosion from the acid rain eating through the endless, slowly regenerating, limestone throughout the planet. Burrowing creatures are rare, for a subterranean environment. Most monsters work through slowly and methodically carving out a niche for themselves, not blasting through rock with jaws of steel.
The unending threat of this planet is the acid eroding it's way into the cave system, causing collapses, floods, and dissolution. There is little to be done for this except to retreat into other areas of The Cave. The much more prescient threats are the spirits of possession which make up the majority of the monsters in this world. A dragon on this world is often born of a humanoid drinking contaminated water, which causes the victim to slowly calcify until it's skin is stone and it is driven to reproduce by contaminating more water. Think of a slow-spreading Zombie Apocalypse of Dragons.
There are six major Geologic regions into which the cave stretches: The Lake District, which has massive basins of clean water filtered out of the acid via extensive calcite boxwork; The Glasslands, regions of volcanic intrusions that were rapidly cooled into wide and shallow planes of obsidian; The Putty Park, which catches much of the dissolved effluent from up above and has twists and mounds made of slick sediment; The Flashflares, which is a region characterized by pockets of magma and caverns full of explosive methane gas; The Dustbowl, which is a region known for it's lack of water due to it's distance from the Tartarus and it's thick roof protecting it from surface floods; and lastly Tartarus, the center of the world, where living shadows writhe and dragon spirits spawn.
This is best thought of not as a cavern, but as a massive fault line. Stretching the surface in some sections, this ravine looks like it was sliced by a heavenly sword. This to the West of this ridge are The Glasslands, which sit approximately 40 feet below their ceiling and stretch on for many miles. To the East are the liminal twisting caverns that connect all spaces. Many claim these nondescript tunnels have false walls and unnatural chasms through which people can clip into otherworldly lands. Regardless, about 15% of these liminal tunnels are within 60 vertical feet of the floor of The Glasslands. Many of these have anywhere from trickles to torrents of acid pouring from the surface between them and The Glasslands. The chasm seems to lead to Tartarus, though falling into the dark is not an immediate death sentence, as the gravity in Tartarus is incredibly weak, it is often an inevitable one.
This cavern marks the boundary between what is known, the Lake District, and what is profane, Tartarus. The Drakelords, a regiment of holy warriors, have taken up residence in this cavern, which is 50 feet wide and 40 feet deep. There are 10 feet of dry stone next to the lake in the main cavern, but periphery entrances and exits provide spaces for about a hundred individuals to live in close quarters. These fearless guardians defend the rest of the lake district from the creatures and spirits that would worm their way out of Tartarus through Lake Draconis. The only entrance to these chambers for humanoids is the Boxwork Chimney, a 40 foot long chute of sharp calcite ledges forming a rough and dangerous ladder. Supplies can be lowered through Isin's Esophagus in a neighboring chamber, but the Boxwork Chimney is the main thoroughfare.
The scintilating site of Zebra Rock has driven many a man and monster alike to utter madness. Zebra rocks are vaulted ceilings, usually small, in which white and black rock has sedimented and deformed into ever-growing eye-numbing concentric rings. Some men claim that praying beneath a Zebra Rock brings an awareness inaccessible to the ordinary people of Draconis. Shamans and hermits are known to take up residence beneath these domes, where they meditate constantly while basking in the scintillating patterns. These sites are a necessity in the creation of magical items, making sociable shamans an invaluable resource for the production of food and purification of water.
The spikes of Spindleton are known throughout Draconis. Miniscule, needle-like threads of gypsum form naturally from the precipitation of dissolved limestone. Oftentimes, these sharp spikes are all but invisible to those traversing Spindleton. Unfortunately, for the people of Draconis, Spindleton surrounds the spawning grounds of the Glow Worms. These silkworms produce most of the light and textile material used throughout the caves. They spawn regularly and must be retrieved to be of any use. Spindleton is home to the town of Spindlespire, one of the few true bastions of civilization. Carved out by Dwarves long ago, the town of Spindleton spends considerable resources clearing tunnels for distant residents to reach the spawning grounds safely.
A sage, sitting beneath his Zebra Dome, has come to the conclusion that his neighboring town, for which he crafts magic items, is best kept safe if they never again access Spindleton. He begins collapsing vital passages towards the Spawning Grounds. He has animated the stalactites and stalagmites themselves to protect him from the "misguided mobs" who try to stop him. The lights are starting to go out, and the clothes are wearing thin. An infusion of new silk is required. Stop the Sage or make safe a secret path to Spindleton that the Sage can never discover.
The shadows of Tartarus are refusing to die. For time immemorial the shadows invading from below have been fought back with light, love, and incredible violence, but now they are persisting, attaching themselves to the nearest living person upon death. While usually shadows possess their victims, these shells are merely attaching themselves and whispering twisted truths to them. They seem far less bestial than most shadows from Tartarus, and are focused on making their victims procreate. One of their victims is now about to give birth. Her attached shadow has begun to shrink. The town fears what will emerge.
Acid is leaking in from high above the city of Spindlespire. The council is terrified that these leaks will give way to a torrent, destroy the spawning grounds, and plunge Draconis into darkness forever. They have offered tremendous wealth to whomever is so daring as to venture into the unexplored, spike-filled tunnels above the town to seek out this leak and divert the acid.
A researcher seeking to understand what nutrients the spirits of Tartarus feed upon is the sole surviving member of his expedition. Stabbed through the arm and bleeding to death, he desperately plunged his arm into the water to seek survival. The water was tainted. He is becoming a dragon. Unlike most, his memory and communication are maintaining themselves, though his body is acting on it's own. He has fled the Drakelords' custody and fled into the dark of Tartarus, swearing that he would return and taint all the waters of the world when his apotheosis was complete. Your goal: venture into Tartarus, the land of shadows, and thwart this would-be despot.