 The story begins on the planet Arth , a haven for the survivors of the Old Empire . Due to heavy radiation , the inhabitants have been forced to live beneath the planet 's crust for centuries . In recent times , the radiation has finally dissipated from the surface , allowing the population to unearth long @-@ lost technology belonging to Arth 's original settlers . The inhabitants of Arth have recently discovered two things : first , that they were once a colony world of Earth ; and second , Endurium , a crystalline mineral that fuels interstellar flight . 
