The Horus Heresy is a cornerstone event in the far future fictional universe created by Games Workshop as the campaign setting for its Warhammer 40,000 miniatures wargame. It is a relatively short but devastating galaxy-spanning civil war that engulfs the nascent galactic empire of the Imperium of Man early in the 31st millennium of the universe timeline; the war is a major cause of the science fantasy universe's dystopian environment. Initially described in wargame supplements published in 1988, and used as the setting for a 1989 Epic-branded tabletop miniatures wargame, it has been utilised since as background for several of Game Workshop's products.