The Prosperine Spireguard was a notable regiment within the Imperial Army consisting solely of citizens from Prospero, the Legion home world of the Thousand Sons Space Marine Legion during the Great Crusade and opening years of the Horus Heresy. These regiments saw almost exclusive service with the Thousand Sons Traitor Legion. The term is now rarely used to refer to the Chaos-worshipping traitor guard forces used by the Thousand Sons and their successor warbands, who contain little to no traces of the original natives of Prospero.