Theras, a prophet of the male persuasion, held the inaugural leadership position within the Theran Listeners. This organization, grounded in the Force, functioned on the planet known as Nam Chorios. During one of Theras' sleeping episodes, the Tsils, a species of sentient crystals indigenous to Nam Chorios, infiltrated his dreams. These Tsils manipulated Theras, instilling in him the conviction that interaction between Nam Chorios and the greater galaxy was undesirable. Subsequently, Theras decreed a ban on the landing of any starship capable of mounting substantial shielding on Nam Chorios.