Thousand Sons - Legio Auxilia Forces: The Thousand Sons maintained a number of Imperial Army regiments raised from the population of their homeworld of Prospero. These regiments aided in the defence of that world like traditional Planetary Defence Forces, while also providing support for the Thousand Sons expeditionary fleets during the campaigns of the Great Crusade. All of these forces were lost to the Loyalist assault during the Burning of Prospero:Prosperine Guard - The Prosperine Guard was comprised of three distinct bodies; the Spireguard, Airguard and Expeditionary regiments. The Prosperine Guard regiments were outfitted to various standards, but in all cases were considered well-trained and equipped, equivalents to the elite Solar Auxilia regiments. Estimates place some 85,000 soldiers within the various barracks and training facilities of the Prosperine capital city of Tizca and smaller outposts scattered across Prospero at the time of the Fall of Prospero.Prosperine Spireguard - The primary Imperial Army regiment of elite Solar Auxilia tasked with the defence of Prospero. There were some survivors of the Spireguard who were present at the Pyramid of Photep at the conclusion of the First Battle of Prospero and were likely transported with the surviving Thousand Sons into the Eye of Terror. Their fates remain unknown.Skyguard Air Command - Prospero's primary air force. They launched every squadron of their two-man anti-gravity skimmers from their hangars to the south of Tizca. Armed with Heat Lances and Missile Pods, their disc-like aircraft duelled for supremacy with the Loyalist forces above the skies of Tizca. It is assumed that they were annihilated in the ensuing conflict.Palatine GuardsNorthern Palatine Guard - This Imperial Army regiment, under the command of Colonel Katon Aphea, was deployed on the edges of the burning port of Old Tizca, which occupied the high parapets of the overlooking libraries and galleries of the Nephrate District. The Northern Palatine Guard were overran by Leman Russ and his Space Wolves in less than two solar minutes during the Burning of Prospero.15th Prosperine Assault Infantry - The 15th Prosperine Assault Infantry was an Imperial Army regiment under the command of Captain Sokhem Vithara. They defended the old eastern quarter of the capital city, known as "Old Tizca," from the initial ground attack of the Space Wolves Legion.Prospero Assault Pioneers - The Prospero Assault Pioneers were an Imperial Army regiment that rallied in defence of their homeworld after the majority of their regiment was wiped out when three of their four barracks were destroyed in the initial orbital bombardment by the Imperial Retribution Fleet. It is assumed that they were slain to a man during the battle.Zhao-Arkhad Taghmata - The defence forces of the autonomous Zhao-Arkhad collective were present within their enclave in the wilderness of Prospero as part of a treaty for the supply of the Legion the Thousand Sons had made with the Mechanicum of Zhao-Arkhad. Consisting mainly of various combat-automata and other mechanised units, numbering perhaps 8,000 warriors and automata. Almost none of these were present within the city of Tizca and dwelt within the subterranean Geller Field-screened fane.Legio Xestobiax - A full vigil of the Legio Xestobiax Titan Legion was stationed within the Zhao-Arkhad enclave, comprising some twelve Titans of varying marks. As with their Zhao-Arkhad overlords, the Prosperine vigil of the Legio Xestobiax was stationed outside the city of Tizca and ensconced in vast underground bunkers in their enclave.Citizen Militia Regiments - In theory, a large percentage of the adult population of Tizca could be marshalled for war and issued weapons from the reserve armouries scattered throughout the city, creating a force of men-at-arms numbering in the millions. However, in practice such a force was of negligible strategic value considering its lack of training and effective leadership.