Cults of the Thousand Sons - Pre-Heresy Cults: Though some Thousand Sons Astartes never developed any measurable amount of psychic ability after being implanted with the XVth Legion's gene-seed, the majority did develop some form of psychic ability just like their Primarch Magnus the Red soon after completing the transformation process.The Legion used these five different cults to develop and improve the abilities of the often powerful psykers found amidst this Legion's ranks.Membership within these cults was determined regardless of the Fellowship (Chapter) to which each Astartes belonged within the Legion since cult membership was based upon the psychic ability for which a Thousand Sons Astartes displayed the most affinity.Each Fellowship of the Thousand Sons was usually made up of Astartes coming from all five of the cults within the XVth Legion, though it was not unheard of for a Fellowship's membership to be dominated by the members of just one of the cults.The five cults had been founded within the Legion by the nine original members of Magnus the Red's inner circle or cabal who were collectively known as the Rehati. The Rehati had each earned mastery in one of the 5 recognised psychic disciplines.Each cult was formed to further the development of one of the recognised psychic aptitudes: the Athanaeans focused on telepathy, the Corvidae sought to develop their precognitive abilities, the Pavoni learned to make use of physiokinesis, the mental manipulation of one's own physiological processes, the Pyrae plumbed the secrets of fire, a discipline called pyrokinesis, and the Raptora mastered the potent power of telekinesis.The leader of each cult bore the rank of Magister Templi. The leader of all the cults was known as the Magus and this was a rank exclusively held by the XVth Legion's primarch, Magnus the Red.The highest rank within the cult system was that of Ipissumus, a grade which represented a being free from limitations, who lives in balance with the corporeal and incorporeal universe. For all intents and purposes, the Ipisssumus was the most perfect being in the universe. This esteemed rank was represented by the most powerful Human psyker in existence -- the Emperor of Mankind.On the Thousand Sons' lost homeworld of Prospero, in the capital city of Tizca, each cult maintained its own pyramidal headquarters, which served as both a repository of the arcane knowledge that they had collected about their chosen psychic disciplines from across the galaxy as well as training facilities specifically geared towards enhancing psykers who displayed strength in one of the five recognised psychic disciplines.Each of these pyramids' front gates was topped by the great golden icon that represented the cult, save for the pyramid of the Pyrae Cult, which was topped by an ever-burning flame and whose gate was guarded by Canis Vertex, a Warlord-class Battle Titan of the Legio Astorum that would see action during the Burning of Prospero.To further represent the distinctiveness of the Cults' members, the Astartes from each cult would display the cult's insignia upon the shoulder plates of their Power Armour, with the cult's distinctive icon placed within the centre of the XVth Legion's Pre-Heresy Legion badge. The five known cults of the Pre-Heresy Thousand Sons Legion are described below.