The Struggle for Crystals

This world is divided into two realms: the upper realm, the Celestial Realm, and the lower realm, the Terrestrial Realm. The Celestial Realm hangs above the Terrestrial Realm and relies on an energy source called crystal stones from below to stay afloat. Without them, it will crash into the Terrestrial Realm, destroying both realms. Under these circumstances, the two realms have fought over crystal stones for ten thousand years.