Cults of the Thousand Sons - Post-Heresy Cults: After the casting of the Rubric of Ahriman, the confluence of once-noble fellowships that comprised the XVth Legion was replaced by a hierarchy born of Magnus' will. The Thousand Sons were divided into nine great cults, each devoted to a separate facet of the Change God, and whether wittingly or not these cults all serve Magnus, and all have a purpose in the unfathomable plans of Tzeentch.Though the Planet of the Sorcerers to which the Thousand Sons were exiled after the Fall of Prospero is a world in constant flux, its inhabitants are governed by a strict order set in place by Magnus. The spectral remnants of the Legion's warriors, known as the Rubricae, reign over throngs of Chaos Cultists, Tzaangors and mutated Warp beasts, while above the Rubricae is the former bodyguard of the Crimson King, known as the Sekhmet.Raised above all of these is the Rehati -- a coven of nine Exalted Sorcerers and Daemon Princes who are favoured by Tzeentch more than any other amongst the Thousand Sons, save Magnus himself.From this overarching hierarchy, the Legion's forces are now further divided into nine cults. At the head of each is a member of the Rehati who bears the ancient rank of Magister Templi. Beneath each Magister Templi are nine other Daemon Princes and Sorcerers who, though lesser in rank, still bear much of Tzeentch's favour. These nine steer the cult along the ever-changing paths of fate.Other Sorcerers hold lower positions in the cult, and along with troops, tanks, mutants and Daemon Engines are capable of claiming vast swathes of realspace for their cult masters. Each cult has worlds from which they draw resources and magical energy, and populous planets to provide them with constant streams of Cultist soldiers, slaves and subjects for their arcane experiments.Aside from constituting a terrifying military force, each of the cults is an amalgam of the twisted minds of those in its ranks, and though inherently self-serving, the members of a given cult are ultimately bent towards the same purpose. To a mortal mind, untouched by Tzeentch's corruptions, the complex plans laid out by these cults are utterly unfathomable, but to the Thousand Sons they are both a form of profane worship and a route to vengeance over the Imperium of Man.Often, the goals of a given cult will undermine or even contradict those of the other cults. As such, the cults are wary of one another, and alliances between them are ever-shifting. The power and influence of each is also in constant flux, with every cult going through cycles of activity and torpidity as befits their inscrutable machinations.It is extremely rare for the entirety of a cult to deploy in a single war zone, though when this does happen the fabric of reality quakes in their presence. More often, the cult's malevolent goals require its forces to be spread throughout space and time, allowing each splinter to play a separate role in some larger and more sinister stratagem. A cult therefore comprises many sects, each of which may prosecute their own seemingly unconnected campaigns of terror.Where the combined forces of a cult could easily set a whole system ablaze, a single sect is still capable of devastating a planet. Often, several sects will launch simultaneous strikes across large tracts of realspace, plunging entire sub-sectors into disarray and panic.As nearby worlds send reinforcements to the embattled planets, more Thousand Sons appear to attack where defences have been stretched to breaking point. Devastating as they are, these attacks rarely give any clue as to the ultimate goals of the cult.A sect is made up of multiple warbands, called "thrallbands" within the Legion, which can also act independently of each other. With several units of Thousand Sons bolstered by auxiliary troops and vehicles, a single thrallband can obliterate an enemy fortress or turn a city into a blazing pyre.A number of thrallbands operate in complete isolation -- some have been exiled from the Planet of the Sorcerers, while others chose to leave to pursue their own ends. But even these forces ultimately serve the goals of one of the nine Thousand Sons cults, whether they themselves know it or not.