The Temple of the Saviour Emperor was one of the many human religious cults which grew up around the worship of the Emperor of Mankind as a god after the Horus Heresy in the 31st and 32nd Millennia. It went on to become the dominant state church of the Imperium, the Adeptus Ministorum or Ecclesiarchy.
However, the theological doctrines of the Temple of the Saviour Emperor, which called for the Ecclesiarchy to dominate every aspect of Imperial politics, fell out of favour during the Age of Apostasy and were reformed by the Ecclesiarch Sebastian Thor and the reborn rival sect of the Temple known as the Confederation of Light in the 36th Millennium.
While the ordinary citizen of the Imperium believes that the Emperor has always been venerated as the immortal and omnipotent god of humanity throughout the history of Mankind, Imperial historians and the Battle-Brothers of the Space Marine Chapters know that this was not always the case. At the beginning of the Emperor's Great Crusade in the late 30th Millennium, the Imperium of Man functioned very differently.
Firstly, there was no Ecclesiarchy, and the veneration of the Emperor, in the form of a cult known as the Lectitio Divinitatus, was frowned upon and outright condemned by the Emperor Himself. The official Imperial doctrine, known as the Imperial Truth, was that the Emperor was an extremely powerful being, the rightful ruler of all Mankind, and the perfect physical, mental and spiritual embodiment of humanity, but no matter how supreme, he was still only a human being.
During the Great Crusade, however, many ordinary Imperial citizens found that the light of reason and truth brought by the Emperor was not enough to fulfill their basic human psychological desires or provide protection from the real supernatural threats that existed in the universe, and so they took to worshiping Him as a deity to fulfill their spiritual needs.
During the Great Crusade, many different religious cults appeared throughout the Imperium worshiping the Emperor of Mankind as a god, each with their own subtle variations and differences in doctrine. These forms of worship appeared first on those primitive planets that had regressed technologically during the Age of Strife. The numbers of these cults multiplied immensely with the Emperor's ultimate sacrifice to save Mankind from the Warmaster Horus during the Horus Heresy and His subsequent incarceration upon the Golden Throne, which was hailed as the Emperor's "ascension" back to full divinity. Most of these cults would gradually fade away, while others prospered, eventually absorbing the weaker ones. The more successful Emperor-worship cults spread their forms of worship to other planets.
The strongest of all the early Imperial cults was the Temple of the Saviour Emperor. This cult had the advantage over the others in that it was based on Terra and that its leader had been a successful and respected officer of the Imperial Army who had fought at the Battle of Terra, defending the heart of the Imperium. This leader had re-named himself "Fatidicus" and had begun to preach his teachings concerning the divinity of the Emperor to anyone who would listen. This faith spread among the members of the Imperial Army and the Armada Imperialis, but also to lowly scribes and minor Adepts of the Imperial Administration (the Administratum). The faith was then spread by these individuals to other worlds. When Fatidicus died at the age of 120 Terran years, the Temple had more than a billion followers on Terra and untold faithful throughout the Imperium's Segmentum Solar.
In the wake of the chaos and anarchy of the Horus Heresy, the Temple of the Saviour Emperor provided a message of hope and reunification through a common faith. Cults who rejected being absorbed, or who couldn't be absorbed, saw themselves being persecuted by fanatical mobs who preferred the Saviour Emperor theology. Officially, the Temple rejected this violence performed in its name.
This development culminated in the early 32nd Millennium, by which time almost two-thirds of the Imperium's population followed the teachings of the Temple of the Saviour Emperor, the exceptions being the Space Marines, who have never formally acknowledged the divinity of the Emperor in line with His wishes and the Adeptus Mechanicus, who had their own form of worship in the Cult Mechanicus. The Temple's importance, influence, and power rapidly outmatched any other Imperial sect dedicated to Emperor-worship.
The Emperor had become an object of general religious veneration across the Imperium following the Horus Heresy and His internment within the Golden Throne on Terra. Over the solar decades after that conflict many individual Imperial cults sprang up throughout the Imperium, with their central theme being the redemption of humanity through the Emperor's self-sacrifice. After a few hundred Terran years, a single church known as the Ecclesiarchy was formed from the unification of a number of smaller cults with the Temple of the Saviour Emperor, which gradually absorbed the main body of diverse believers in the Emperor's divinity.
In the 32nd Millennium this cult was finally recognised as the official state religion of the Imperium, granted the official governmental title of the "Adeptus Ministorum" and incorporated into the Adeptus Terra once the High Lords realized how useful the religion could be in protecting, unifying and energising the citizens of the Imperium from the myriad dangers of the galaxy. Remaining religious cults which differed in their primary theology from the Imperial Creed taught by the Ecclesiarchy were persecuted and mostly destroyed by the first of the Wars of Faith called by the Ministorum.
A few centuries later, in the middle of the 32nd Millennium, Ecclesiarch Veneris II received a seat amongst the High Lords of Terra, and after 300 Terran years, this seat was made permanent. The political power of the Ecclesiarchy continued to grow, increasing its hold over the minds and beliefs of the Imperial citizenry. Those who would not follow its teachings were declared unbelievers and Heretics, ostracized, and on occasion even executed.
The vast interstellar territories of the Imperium were organised into dioceses led by the Ecclesiarchy's Cardinals. These powerful religious and political figures were responsible for Missionaries and Preachers on hundreds of worlds.
Lavish shrines, impressive temples, and majestic cathedrals dedicated to the God-Emperor of Mankind were built throughout the Imperium. Millions of religious pilgrims soon began making their way across the galaxy to visit particularly important religious locations, such as the world where a particular Imperial Saint had performed their most famous miracle.
In time, the sheer number of pilgrims who arrived on certain worlds became an economic activity in itself and entire planets were dedicated to worship and directly ruled by the Adeptus Ministorum as Shrine Worlds. Particularly important Shrine Worlds could become the religious seat of an entire diocese and so a Cardinal would take up residence there. These planets became known as Cardinal worlds.
The only threat to the domination of the Ecclesiarchy was the Confederation of Light. Based upon the planet Dimmamar, this penitent sect's ideals of poverty, selflessness and humble living clearly contradicted the teachings of the Ecclesiarchy, whose view was that sacrifices of wealth and money to the Adeptus Ministorum in taxes, tithes and other gifts were necessary to enhance Imperial citizens' access to salvation and ensure that the Emperor's light reached every corner of the galaxy through His missions.
In truth, the Confederation's theology directly opposed the efforts of the Ecclesiarch and the Cardinals in their attempts to ensure that the Ecclesiarchy remained the wealthiest and most politically powerful institution of the Imperium.
The Confederation proved too difficult for Ministorum agents to infiltrate, and the Ecclesiarchy of the time turned to violence, supported in this effort by the unanimous vote of the Senatorum Imperialis of the High Lords of Terra, who declared the onset of the first War of Faith in the 32nd Millennium, largely to ensure that Imperial political stability was not damaged by the emergence of religious plurality.
The entire Confederation was declared heretical and the forces of the Astra Militarum, the Imperial Navy, and thousands of fanatical zealots from the Frateris Militia were unleashed upon it, bent on its destruction. Only a few cells and hidden shrines of the Confederation managed to survive, and the power of the Ecclesiarchy over the minds of men, for better or worse, was made unassailable.
By the end of the 33rd Millennium every Imperial world was furnished with its own cathedral and the coffers of the Ecclesiarchy were filled with the offerings and tithes from the teeming billions of the God-Emperor's faithful. This wealth was squandered by building additional, ever larger and more lavish churches and cathedrals and to fund Wars of Faith intended not to save the souls of humanity but to secure the Ecclesiarchy's political power and wealth.
The Age of Apostasy in the 36th Millennium was one of the most destabilising events in Imperial history after the Horus Heresy, beginning during the long struggle between the Ecclesiarchy and the Administratum for power over the Imperium. High Lord Goge Vandire, the 361st Master of the Administratum, was a power-hungry tyrant who eventually gained direct control over the Ecclesiarchy as well as the Administratum by usurping the position of the Ecclesiarch. This made him the most powerful individual in the Imperium, and allowed him to place his own rule above even that of the Emperor.
His time in power became known as the Reign of Blood, consisting of massive purges of the Ecclesiarchy, and the killings and assassinations of countless perceived Traitors and conspirators. This period was eventually ended by the Ecclesiarch Sebastian Thor's reborn Confederation of Light, a sect of the Imperial Cult that sought to end Goge Vandire's corruption of Imperial theology.
The Apostasy ultimately resulted in a major reformation of the Ecclesiarchy, the creation of the Inquisition's Ordo Hereticus to police those enemies of the Imperium who lay within its own structures and the founding of the Adepta Sororitas to serve as both the Ecclesiarchy's new military forces and the Chamber Militant of the Ordo Hereticus.
The reformation of the Ecclesiarchy also altered its theology, emphasising the Confederation of Light's principles of penitence, self-sacrifice and humility that are recognisable in the religion of the present Imperium in place of the need for political and economic dominance which had driven the Temple's theology.
These principles would replace the "old" era of decadence and greed which was associated with the Temple of the Saviour Emperor.
However, even in the 41st Millennium, there are those within the Ecclesiarchy who exhibit a desire to use the institutions of the Imperial church to gain wealth and political power for their own sake. This has been referred to within the church as having a "tendency towards the Temple" as a warning against returning to the old ways.
Those who are actually found to adhere to the beliefs and practices of the pre-reformation Temple of the Saviour Emperor are regarded as Heretics who have turned their backs upon the current incarnation of the Imperial Creed.
However, there do exist secret cults that actively work against the current Ecclesiarchy in the Emperor's name, in an attempt to return to the old ways as they regard the current religious theology of the Adeptus Ministorum as the true hersy.
These self-declared "Temple Tendency" cults slowly and secretly work to gather military and political might to use against the ministorum and are enough of a threat to be hunted by the Inquisition
- Codex: Sisters of Battle (2nd Edition), pg. 5
- Dark Heresy: Core Rulebook (RPG), pg. 263
- Dark Heresy: Blood of Martyrs (RPG), pp. 18-19
- Dark Heresy: Disciples of the Dark Gods (RPG), pp. 31-39, 198