Thermocline Grotto

The Thermocline Grotto is a high-altitude alpine glacier, the largest such glacier in the known realms of the Material Plane. Its exact size is unknown, but various estimates from historical sources place it anywhere between 30 to 50 miles in diameter at its widest point.   Inside the glacier is a sprawling network of caves and tunnels, with enough space to house the three white dragons of the Katabatic Conclave, their younglings, and their vast treasure hoards. Small streams and waterfalls flow through certain sections of the cave, providing fresh water.

Icy wind rages in the area around the Thermocline Grotto, regardless of the season. Blizzards and hail are frequent year-round. The weather is at its harshest in autumn and winter, and is deadly to most humanoids within less than a day if they are not equipped with heavy protection against the elements. Spring and summer, though less deadly, come with their own dangers, as the slightly warmer temperatures may cause sudden floods or cavern collapses that can easily trap and kill creatures who are not accustomed to glacial caves.

The primary residents of the Thermocline Grotto are the three most ancient white dragons alive at any given time, who form a traditional clan known as the Katabatic Conclave. Their offspring are permitted to live within the caves of the grotto for the first few decades of their lives, but are increasingly antagonized by the older dragons until they leave to find their own lair in the surrounding mountains.   A small colony of frost giants lives near the southern edge of the glacier. They are easily coerced into acting as mercenaries when the Conclave feels the Grotto needs extra protection; in more placid times, though, some of the more powerful frost giants attempt to show dominance by killing younger dragons or kobolds. The few who survive the dragons' retaliatory attacks gain their respect, and are sometimes allowed to serve directly under the dragons in exchange for easy food and protection.   The white kobolds that manifest from these dragons are particularly strange, even among their species. The unique texture of their scales and claws naturally sticks to ice, allowing them to keep their footing where most other creatures could not. Their body temperature is so low that they can be frozen in ice indefinitely without harm, which their draconic masters often do when annoyed by them. The white kobolds are so isolated from mortal society that they do not understand Common. Instead of kobold traps built from found items, they use the icicles, streams, and natural weak points of the ice in the glacier to stop any would-be invaders.   What little plant life survives in the area outside the glacier is tough and woody, and the few creatures adapted to survive in the region (such as great white bears and mountain elk) are more territorial and aggressive than their counterparts further away. The fur of these animals is paler than others of their kind, and their eyes become dragon-like, ranging from gold to orange-red in color with slit pupils.

According to draconic legend, the massive cavern near the base of the grotto was left behind from where Tiamat first carved out the first white dragon Vellundithoer and his tripartite guard. Over the millennia, the glacier has been shaped by time and its inhabitants' frost breath into a mazelike network of tunnels, caves, and secret rooms.   In the times between their power struggles with the other true dragons of Draxhaven, the Katabatic Conclave spends their days shaping and re-shaping the ice to admire the thousands of years worth of treasure frozen within, as well as arguing over which pieces of the hoard belong to which dragon. As they preserve their hoard entirely in ice, there are likely incredibly ancient treasures frozen within the glacial caves that would have otherwise rotted away centuries ago.

Between the dangers of the terrain, the extreme weather, and the cruelty and power of the ancient white dragons, the Thermocline Grotto is one of the deadliest places on the Material Plane. Even experienceddraconologists rarely survive carefully planned scientific expeditions; no Adventurer has been proven to have raided the lair and lived.