as found in the pages of the Zd10 Wiki
The magical art of Terramancy and the practice of it known as Terratheurgy is one of the four most popular magical arts taught across the planes. Terramancy is the arcane manipulation of magic to achieve effects based around stone, metal and gems. They can manipulate many aspects of earth however, including lava, minerals, seismic force to even natural gasses and mud.
As long as people have walked on it and dug underground, a certain respect has been held for the earth. Jewels and gems captivate and fascinate while metals have built and vanquished entire civilizations. Mastering the magical art of Terramancy leads one to a large magical toolkit, ranging from spells of destruction and aid to those that, left unchecked, could possibly destroy metal based economies.
Terramancers don't have a hard time finding work with everything they are capable of. Many find work assisting large scale blacksmiths or even operate smithies on their own. Some find work as prospectors for large trade magnates. In a few cases, some even operate subterranean travel-ways for worlds where the surface is dangerous, or to provide shortcuts across dangerous or difficult features on the surface.
The First Age brought about the first schools and colleges for magic, and Terramancers from many worlds were able to work together to create the unified art of Terramancy. Being one of the oldest forms of magic, Terramancy is a very popular art. Controlling what they walk on and everything underneath is a very promising prospect, though it isn't that rare for those with a heart more for greed to learn Terramancy, thinking that their capability for creating rare and precious metals and gems will grant them some form of power.