| Category | Caverns | ||
| Continent | Brucrumus | ||
| Region | Troll Bogs, Slilp-Urp | ||
| Map |
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Along the southwestern coasts of the Troll Bogs lies a vast network of sea caves and Underdark passages known as Tûnin-Gil. The caves are at sea level and partially submerged in the waters of the Pearl Sea. The caves then extend northward through old lava tubes. After some distance, this area becomes part of the Underdark region Slilp-Urp. For miles into the caves, areas are often illuminated by open-air shafts from long-dead volcanoes, with innumerable sinkholes and vents. An enormous quantity of water cascades into the caves from the swampy lands above. This wetness and the light from the holes foster massive fungal growths on the ceilings and vast clumps of floating vegetation.
Several of the sea entrances are sizable enough to admit vessels. During the Third Epoch, surface realms commenced establishing commercial routes with certain of Slilp-Urp's civilizations. Alongside the trade, Underdark piracy emerged, and the customary disputes over maritime jurisdiction ensued. In addition to the menace of pirates, Tûnin-Gil harbors numerous gargoyles, harpies, and stirges. These creatures roost within the myriad sinkholes, chutes, and crevices spanning the Underdark sea passageways to the surface.
Ten miles into the sea caves lies a mammoth passage leading to Nagdúrzol and the Spire of Rioch Tetrax. During the Horgon Era, these two areas were governed by the Durkoth. Tûnin-Gil's waterways served as a highway to reach potential new subjects. When the Durkoth departed for the depths of the seas, their former minions, primarily Dromites and the Laupha, were left to their own devices. The Laupha, embittered by being confined to the restrictive environment of Tûnin-Gil and the Underdark for so long, were the first to depart the area. Half of the region's Dromites followed suit, heading for the islands of the Buccaneer Archipelago and the Pearl Sea.