The Third Sister (Kilian III) is a protoplanet in the Kilian system, United Empire of Earth (UEE) that orbits the system's sun in the L5 Lagrange point of the hot Jupiter First Sister (Kilian I). Glittering patches of ice can be found dotted across its surface. Because the UEE Navy utilizes the Third Sister as a testing ground for weapons, landing is prohibited without proper military clearance.