| Category | Caverns |
| Continent | Brucrumus |
| Regions | Phangul |
| Map | Sygning |
Hlat'tar is a massive cavern of Sygning. Into the early years of the First Epoch, this cavern held a deep lake that was home to the Aboleth. Suffering slaving, raids, and outright war, the drow of Filion'lyr hatched a bold plan. They built a lock system that over two decades drained the lake, leaving two aboleth city-states exposed to naval bombardment and easier reach. Besieged, the drow then poisoned and fouled the shallow lakes around the enemy's half-submerged cities. The drow did not let up, with the last of Hlat'tar's aboleth put down on 19 Hollow 261.
Hlat'tar is cut by the River of Vuzlyn. When the Filion'lyr opened The Mandible, draining the lake, this river bored a new channel. This new channel and much lower water level left many pools, wetlands and two small lakes around the ruins of Azoloch and Gon'tora. A very damp area with continuous dripping from above, Hlat'tar is a verdant landscape of subterranean plants and lifeforms. In the south, near the city of Filion'lyr, are vast farmlands tended by myconid and their drow overseers.
Along the northwestern axis of the Great Tradeway, most goods and people move through this area by boat; avoiding the area's many shambling mounds, oozes and the occasional undead aboleth.