From the introduction:
Remnant [the setting of RWBY] is a world where Man was brought to the brink of extinction. Driven back by the creatures of darkness known as Grimm, Man was nearly helpless. However, in time Man’s ingenuity led to the development of Dust. Dust is nature’s wrath in physical form, and with Dust, Man could bend the forces of nature, and by extension, the creatures of Grimm to his will. In the time since, great Huntsmen and Huntresses have been selected and trained to protect Man and all his kingdoms from the creatures of Grimm, who are always ready to strike and the first sign of weakness, and destroy Man forever.
An "unofficial" adaptation of the media series to tabletop gaming.