Tildon Deep is a great undersea chasm of the Sea of Mourning. In the northeastern part of this area is the caldera of an ancient volcano. It is one mile wide and descends nearly three miles down. The volcano is dormant which is fortunate for the sahuagin and other aquatic creatures living in T'kyr. This city is sited at the bottom of this ancient volcano.
The surface, above the chasm, is a major sea lane for ships of many flags. The evil creatures of Tildon Deep are a common threat to passing ships.