Rift in the Ishnit Jungles. Absurdly deep—all the way to the center of the material plane.
The Naruaghin who live in the surrounding jungle are terrified of the pit, and won't go near it.
Occasionally, thinsgs emerge from the pit. Animals brutally killed and left to rot on outside edge of cliff. a mile down, and 30 miles north-east, is a location where someone has devoted their life to the study of darkness. It is within the rift, but deep, deep inside.
The rift extends at a diagonal much further than you can tell from map—jungle has just grown over it. Shadows sometimes come up from the cracks.