Long ago, a war was waged between the forces of darkness and light as Dark Brings--stones containing dark power beyond human ability--put the world at risk with their destructive force. In order to stem the tide of darkness, a lone swordsman used holy power known as the Rave to destroy the source of every Dark Brings. The resulting explosion, which came to be known as the Overdrive, destroyed a tenth of the world; fragments of the Rave were scattered throughout. (myanimelist.net)