The Terahnee are a race of humanoid aliens who are descended from the Ronay They relocated to the Age of Terahnee approximately 9,700 years ago to escape the destruction of their original home world, Garternay. They are also cousins of the D'ni, who fled the same cataclysm by relocating to Earth.
"Terahnee" (teranE) is an abbreviated Ronay/D'ni phrase meaning "new tree". The Terahnee are descendants of the majority of Ronay refugees. On Terahnee, they maintained the lifestyle and culture of their original home world.
Unlike the D'ni, the Terahnee also maintained their belief that regestoy—the "Art of Writing"—was a skill that made them superior to the peoples of the Ages to which they linked. They built their entire civilization on the brutal subjugation and enslavement of thousands of other worlds.
Because they are descended from the same ancestors, the Terahnee have similar lifespans (approximately 350 years, on average) and physical attributes as the D'ni. They are physically indistinguishable from humans, but often have taller and more slender build. Unlike the D'ni, they live on the surface of their world, and so have not developed the same sensitivity to bright sunlight.
After over 8,000 years of separation, the Terahnee and the D'ni were briefly reunited in the 9460s DE with devastating consequences. Atrus and his companions discovered the Age while attempting to rebuild the D'ni city, and chose to send a small expedition to explore it. Unbeknownst to them, they carried a stomach bacterium with them that proved to be almost universally lethal to the Terahnee. Within weeks of their arrival, over 99% of the Terahnee were dead. In a nation of over 200 million, fewer than 100,000 survived.