Treaty of Mars - Emperor of Mankind Comes to Mars: When the Emperor of Mankind finished uniting the feral techno-barbarian tribes of Terra during the Unification Wars in 712.M30, He was already aware of the existence of the Cult Mechanicus on Mars and the vast, if fractured stellar empire it had colonised.Realising that waging war against Mars and bringing the Cult Mechanicus to heel with His new Imperium and its atheist Imperial Truth would be a long and wasteful battle, the Emperor journeyed to Mars in peace with an outstretched hand and made first contact with the people of the Machine Cult in 739.M30 at the summit of Olympus Mons, the greatest mountain of the Red Planet.When the Emperor first emerged from the ancient and refurbished Terran voidship he had crossed to Mars in, surrounded by all the glory and magnificence His psychic abilities could conjure, many of the Mechanicum's Tech-priests present immediately believed Him to be the Omnissiah, the mortal incarnation of the Machine God long promised by Cult Mechanicus prophecy.The Emperor eventually earned an audience before the Mechanicum's parliament of governing magi led by their Fabricator-General. The arrival of the Emperor set off political turmoil across the Red Planet, for having expunged any trace of mutation in their own gene-stock long before, the Martians were at a loss to explain the glory of the immensely powerful psyker who strode amongst them.Capitalising on this, the Emperor spoke of the legendary times long past in the Age of Technology when Terra and Mars had worked together to form the core of an illustrious interstellar Human federation, and told the Martians that He intended to build a new Golden Age for Mankind in the form of His nascent Imperium of Man.To this end, the Emperor invited the Martians to join Him, proposing to them the terms of a generous alliance backed up by the veiled threat that He would unleash His genetically-enhanced transhuman warriors of the Legiones Astartes upon the Red Planet if the magi refused Him. The Imperial proposal granted political autonomy to the Mechanicum of Mars and its Forge Worlds scattered across the galaxy as well as an exception to the atheistic Imperial Truth so that the Cult Mechanicus' adherents could continue to practice their faith.The Imperium would provide six houses of Navigators and its astropaths to the Mechanicum so that it could unite its far-flung empire of lost Forge Worlds and continue its sacred Quest for Knowledge more easily across the galaxy. In exchange, the Mechanicum would supply the Imperium with the weapons, voidships, materiel, engineers and technicians required to initiate the Emperor's Great Crusade to reunite all of the Human-settled galaxy beneath the banner of the Imperium.The Martians, realising they had much to win by placating the Emperor, and even more to lose if they opposed Him, agreed to the terms of the proposed alliance after some bloody internal strife, an agreement aided by the reality that many amongst the Mechanicum already believed Him to be the Omnissiah.Unable to abandon the religion which defined their existence, the Martians proposed a compromise that the Emperor agreed to with some reluctance: He would be presented to the masses of the Cult Mechanicus as the Omnissiah, the living incarnation of the Machine God, the long-awaited living repository of all knowledge and wisdom who incarnated all of the values of the cult. Despite being a direct contradiction to the Imperial Truth, the Emperor understood that being presented as the avatar of a god was an acceptable evil in order to secure the Cult Mechanicus' assistance, and that attempting to force the Mechanicum to accept the Imperial Truth could wait until the end of the Great Crusade.At the same time, the Emperor imposed an exigence of His own upon the Mechanicum. Well aware of the sad story of the Men of Iron, the "false minds" who ruled the Martian surface during the early Age of Strife and the inherent danger and vulnerability of certain technologies to the corrupting influence of Chaos, He forbade the Mechanicum to pursue certain types of knowledge, foremost amongst those the development or study of Silica Animus; machines that possessed full self-awareness and were totally independent of Human control.The Emperor listed a number of machines and technological concepts that could lead to the combination of technology with the sorcery of Chaos, and ordered those subjects to be considered taboo, and not to be researched by the Tech-priests under pain of execution. Since many such forbidden technologies already existed in various magi's forge cities or lay hidden beneath the sands of Mars, the Emperor ordered the ruling Fabricator-General of the Mechanicum to seal all such devices within a special cache that only He or His trusted representatives could open, known as the Vaults of Moravec.The Mechanicum grudgingly acquiesced to this arrangement, but the restraint on the Tech-priests' sacred Quest for Knowledge, even the pursuit of dangerous knowledge, would create festering resentments within the Cult Mechanicus that would later reemerge during the Horus Heresy over 200 standard years later.The terms of this political and economic alliance were then formalised in a binding agreement called the Treaty of Mars, known as the Treaty of Olympus Mons to the Tech-priests after the place on the Red Planet where the Emperor had first trod their soil. This treaty would inextricably bind together the Imperium and the Cult Mechanicus for the next ten standard millennia.To symbolise the alliance created between Terra and Mars that marked the true birth of the new Imperium of Man, the Emperor changed His personal sigil from one of a raptor and lightning bolt, the Raptor Imperialis, to the Aquila, a two-headed eagle whose heads represented the twin foundations of the new Human interstellar government -- Terra and Mars, Imperium and Mechanicum.Although this foundational alliance was later threatened during the Horus Heresy and the Schism of Mars, it ultimately endured across the millennia.In the 41st Millennium, the Mechanicum, now known as the Adeptus Mechanicus in the wake of the purge of its Traitor elements during the Horus Heresy, is still an almost autonomous entity within the Imperium, spared most of the attention of the Adeptus Ministorum and Inquisition by the dictates of this ancient treaty which laid the very foundation of the Imperium.