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.
Formed from the natives of Magnus' homeworld of Prospero, the Prosperine Spireguard took part as an auxiliary force in several campaigns for the Thousand Sons before and after the Horus Heresy. Those who did not join in the expeditionary fleets of the Thousand Sons were instead used as a defensive force for Prospero itself. When the Thousand Sons were forced to fight the Space Wolves and turn their backs on the Emperor of Mankind during the Fall of Prospero, the Prosperine Spireguard were quick to join, not aware of the reasoning behind the attack on their planet.
During the First Battle of the Fang in the 32nd Millennium, where the Daemon Primarch Magnus the Red led his Thousand Sons to the Space Wolves' home world of Fenris, most of the post-heresy Spireguard forces were slain. It is not known whether or not fragments may still exist of the original Spireguard within the ranks of the Thousand Sons, kept alive by the unnatural powers of the Chaos Sorcerers so common within the Traitor Legions or the fell powers of the Chaos Gods.
- Fall of Prospero (004.M31) - Following the Council of Nikaea, Magnus the Red, Primarch of the Thousand Sons Space Marine Legion, was ordered to cease the use of psyker abilities within his legion. Despite this edict from the Emperor, Magnus continued his research, leading him to send a warning to the Emperor when the coming heresy became clear to him. This mistake, which damaged the Emperor's Imperial Webway project, and the manipulations of Horus, Primarch of the Sons of Horus, led to the Emperor dispatching a punitive fleet of the vengeful Space Wolves Legion, led by Leman Russ, to attack Prospero itself. In the battle that followed, a large majority of the Prosperine Spireguard died, having little chance against the greater strength of the The Rout. However it does appear that some were able to escape with the Thousand Sons to the Planet of the Sorcerers, where their service to a now-corrupted Magnus the Red would continue.
- First Battle of The Fang (742.M32) - Following the Horus Heresy, Magnus the Red led a massive force of the Thousand Sons in an attack on The Fang, the mighty fortress-monastery of the Space Wolves on their homeworld of Fenris. Several times Magnus appeared to the Great Wolf Harek Ironhelm in visions amongst the ruins of devastated cities that had been laid to ruin by the Thousand Sons Traitor Legion striking from out of the Eye of Terror and taunted the Great Wolf for his inability to stop him. Harek had become obsessed with bringing their old rivals into open battle. Pursuing a rumour that the Thousand Sons maintained a secret base on the world of Gangava near the Eye of Terror, the Space Wolves launched a full-scale planetary assault against it. This was a deception intended to draw the bulk of the Space Wolves' forces from their homeworld, leaving it undefended; for in truth Gangava was held by a Chaos force allied to Magnus but it served only as a distraction, intended to draw the Space Wolves away from their homeworld so that a massive Thousand Sons' fleet could besiege Fenris itself. The Space Wolves' fortress-monastery, The Fang, was held by only a small force of Space Wolves and their Servitor-thralls. For forty days and forty nights the Thousand Sons and a large detachment of Prosperine Spireguard assaulted the citadel. Eventually, a the large force of Space Wolves led by the Great Wolf was able to return to Fenris and reclaim their world, though Harek was slain when he faced Magnus in battle. Throughout the fighting which ensued, large swathes of the Spireguard force were killed by the ravaging Space Wolves, along with many of their Thousand Sons Chaos Space Marine masters. The Thousand Sons were ultimately defeated and scattered, the Traitor Legion's warbands forced to return to the Planet of the Sorcerers within the Eye of Terror.
Notable Prospero Spireguard
- Sokhem Vithara - Sokhem was an officer within the Prosperine Spireguard during the end of the Great Crusade and the beginning of the Horus Heresy. He and his company were last reported taking part in the heavy fighting against the Space Wolves during the Fall of Prospero. His true fate is unknown.
- A Thousand Sons (Novel) by Graham McNeill pg. 189-224, 472-522
- Battle of the Fang (Novel) by Chris Wraight