Chaos Cult - Roots of Insanity: Of the seeds of this galaxy-wide chaos, much has been surmised but very little proven. Indeed, it is likely the Warp cults that originally aligned themselves to the Warmaster Horus' cause did so for a wide range of different reasons, although the end result was essentially the same -- anarchy, bloodshed and treachery on a galactic scale.Regardless of the underlying source of the taint, it was the dark genius of the Warmaster's numerous envoys, in particular the Word Bearers' Dark Apostles and their disciples, that harnessed it to the Traitors' cause. No doubt most would have receded over the generations were it not for the far-reaching and horrific scheme of First Chaplain Erebus and his kin, while others would likely have burned themselves out in brief, if bloody, rebellions.One source of the Chaos corruption which led to the formation of many Warp cults was the religiosity of many ancestor populations, suggesting woeful failure in the Imperial Iterators whose task it was to dispel these beliefs and replace them with the Imperial Truth. Indeed, no world should have been declared fully Compliant until this had occurred, hinting at either conspiracy on a monumental scale or gross systemic incompetence.The latter might seem the more plausible theory, but the events of the Horus Heresy indicate the former is all too possible. Regardless, in the aftermath of the Isstvan V betrayal, countless thousands of formerly denounced religions reawakened in subtly altered form.Benevolent deities were supplanted by vengeful gods and offerings of crops replaced with demands for blood sacrifice. All led inexorably to the worship of those Ruinous Powers which came so close to laying the Imperium low.Another source lay in Mankind's own dark nature. Despite the trappings of civilisation and the appointment of Imperial Commanders to rule over them, the populations of a great many Human-settled worlds still existed in barbarous conditions little improved since the Age of Strife. A campaign to bring a primitive Feral World such as Oran or Forman C2 to Imperial Compliance might be won in solar weeks, but it might take solar decades or standard centuries before such a world could support a functional society able to take its place within the Imperium.The populations of these worlds were notoriously warlike and primitive, and it took many generations to educate them in the Imperial Truth, for native ancestral superstitions were never far from the surface of those recently illuminated by the Emperor's light.Similarly, large parts of the populations of many Hive Worlds were violently lawless and resentful of any form of authority. Even the most productive of Hive Worlds were host to countless thousands of wretches who existed in the lightless under-hive depths without ever learning of the Imperial Truth.On worlds such as Gamma-Horgan, Kado and Avellorn, hyper-violent underhive gangers were quick to join with the forces of disorder when the Horus Heresy came to their world, hailing Horus as a leader truly deserving of their loyalty.At the other end of the spectrum were highly-ranked individuals whose positions within the upper echelons of the Imperial expeditionary fleets granted them access to knowledge others were denied. Though many aberrant Human cultures were entirely obliterated, conservators attached to the Great Crusade's fleets strove to record tales of the defeated foes of Mankind, from ravening alien horrors to recalcitrant Human societies.Much of this knowledge was locked securely away and remained accessible only to the most senior of Human and transhuman leaders, for many accounts contradicted the atheistic doctrines of the Imperial Truth and could not be allowed to fall into the hands of the weak or the ignorant.Inevitably however, some did, and many senior conservators were compromised by the events they recounted or the accounts in their custody. Men and women who had dedicated their entire lives to proving primitive superstitions false discovered that their own beliefs in empiricism and rationality were in fact founded upon lies.When the Age of Darkness fell upon the galaxy, the knowledge watched over by many conservators escaped into the hands of madmen and Traitors who preached it to the Warp-slaved multitudes.