From House of Hozz
The Deepening, a city located at the lowest habitable region of the world. A major Zarth stronghold/citidel and center of dragon hunting operations.
So close to the origin of the air, Deepening draws most of its power from the wind. However, the wind is a major hassle as well, and the main factor in the location of The Deepening is where the lowest outcropping can be located to shield the city from the constant blast. Situated below the point where the air seperates into different paths, Deepening also is a hub for messages and transportation, since the wind can carry blimps (sky vines?) with amazing speed to all corners of Zarthaanc. Along with the wind, the dragons come up from the depths, and Deepening is the first line of defense for those who hunt down dragons.
At some point, Fay managed to get below the air seperating point and release Stone-eater spores, which spread throughout Zarthaanc and wreaked havoc among the Zarth mining operations. The idea was to soften the stone and allow the Great Tree to grow roots deeper into the earth. The effort met with mixed results, as the Tree was able to root deeper, but the weakened stone created many cave-ins, and the rushing wind carried much of the soil away, creating huge dust storms above ground and de-stabilizing the landscape, including the Great Tree itself.