Therans were known as "listeners" because of their ability to hear the Tsils speak to them. Because the Therans listen, they were aware of what took place on Nam Chorios. Therans were in charge of keeping the drochs, carriers of the Death Seed, life suckers that sent their victims' life to Dzym on the planet. They accomplished this by protecting huge gun stations that were placed around the planet so that nothing larger than a B-wing can land. Anything larger than a small one-manned fighter would have enough shields to protect drochs from the planet's radiation when it left, and would inadvertently loose the Death Seed out into the galaxy. The Newcomers thought that the Therans were trying to keep the planet's possible export of the programmable "smokies" or "spook crystals" (Tsils) dampened and the planet poor. They did not discover the real reason for the gun stations until Luke Skywalker and Leia Organa Solo came to the planet in 13 ABY and explained it to them during 's invasion.