The skill of sword-fighting is known to two tribes, the Tribes of Light (which consists of humans living on the world's surface) and Shadow (largely part-human-part-animal creatures and monsters living in an underground city, who enjoy a lifespan five times as long as the Tribe of Light and age one-fifth as quickly). The two tribes lived in peace and harmony, their domains separated by the "Words Worth" tablet—a huge monolith slab erected by an almighty creator. Although the tablet has writing on it, neither Tribe can read the text. One day, Words Worth was mysteriously destroyed by an unknown entity; its fragments scattered among the domain of the Tribes of Shadow.