The Treaty of Mars
Following the Unification Wars of ancient Terra, the Emperor of Mankind realized - if his vision of a unified galaxy were to be achieved - he would need to ally with the vast empire of Mars. Not only could he ill-afford the awful war that would be necessary to conquer them, but their technological knowledge and manufacturing capability were essential for his planned Great Crusade. And so it was, perhaps for the first time, the Master of Mankind came in peace, landing atop the greatest mountain of the Red Planet, Olympus Mons, in a golden spaceship. Emerging with all the glory and majesty his vast psychic power could conjure, he came to treat with the Cult Mechanicus.
The Emperor's penetrating intellect, deep and wide-ranging knowledge, and seemingly-supernatural power - repairing a damaged Knight-Titan with but a touch - awed the Martians. Having expunged all mutations from their gene-stock millennia before, they had no frame of reference for the Emperor's psychic might, and so many of them came to worship him as the Omnissiah, the living incarnation of the Machine God. It was as the Omnissiah that the Emperor was presented to the masses of Mars, allowing the Treaty of Olympus Mons to be signed.
One of the first members of the Cult Mechanicus to herald the Emperor as the Omnissiah was a young tech-priestess called Verity. Ironically enough, this is likely a pseudonym, her true name having been lost over the ages. Her specialty and focus was cogitators and their logic-circuits, and she was a member of sub-cult who understood the Quest for Knowledge not only explicitly as a quest for truth, but also a quest against falsehood, deception and deceit. Those who had come before her had labored to create not only evidence-weighing and conclusion-deriving cogitators and logic-engines, but also specialized auspices capable of detecting the physiological and neurological signs of lying in an unaugmented human. She herself had refined these sensors, integrating them into her own augmented body together with sophisticated algorithms imprinted on crystalline circuits which left her unable to lie or be lied to.
In the Emperor, she saw the Omnissiah, the avatar of the Machine God, and venerated him without question. Her superior, a senior Magos of the Cult Mechanicus, was to be present during the signing of the Treaty of Mars, and she mustered the most impassioned entreaties her logic-circuits would allow her to make that she be named to his entourage. Impressed by her argument - or perhaps some fragment of humanity was swayed by the young woman's passion seeping through logic-nets - he allowed her to accompany him. In an vast chamber where a thousand vox-servitors sang the hymns of ignition beneath a hydraulically-operated crystal dome, the Emperor and the Fabricator-General signed the treaty and affixed their gene-seals to the document. Afterwards, the attendant Magi and their retinues were brought before an increasingly-uncomfortable Emperor, there to venerate him as the Omnissiah.
Verity, standing before the Master of Mankind, was the first to pledge not merely allegiance to him but offer to accompany him and his armies on the Great Crusade across the galaxy. Stired perhaps by some difference in her manner, the Emperor listened as she spoke eloquently of the virtue of truth rather than mere knowledge, and the dangers of falsehood and deceit. When her superior attempted to pull Verity away, the Emperor stayed him with a gesture and urged her to continue.
Who can understand the mind of a god? Certainly not Verity, but can it be said the Emperor understood her either? She was a devotee of the Machine God, a woman of fierce religious fervor, and he was the Emperor of Mankind, the author and enforcer of the atheistic Imperial Truth. She worshiped him as the divine avatar of her god, he denied the very idea of divinity. It was impossible what she meant by seeking truth and exposing falsehoods aligned with his understanding. Yet he not only listened to her, but smiled benevolently and nodded encouragement.
The technobility of Mars had always understood the Emperor would need more than war materiel produced by their forges, and that they would receive in return something greater than mere tolerance and the staying of the sword of the Astartes. He would need their tech-priests to accompany his armies on the Great Crusade, to tend to all the engines of war they would provide. And, in turn, the Quest for Knowledge would travel faster and further than ever before, protected by the mighty military of the nascent Imperium of Man. This had not only been understood, but part of the Treaty of Olympus Mons, and so while Verity showed temerity, her request was at least logical.
But the Emperor surprised everyone - the technobility of Mars from the Fabricator-General down to the lowliest Vice-Magos, his own entourage from Captain-General Valdor of the Custodes and Malcador the Sigilite down to the humblest scribe recording every word and gesture for posterity - by personally selecting Verity to not only accompany the Crusade, but to join his entourage. Other tech-priests would accompany the Emperor and align the Quest for Knowledge with the Great Crusade, but it was not for her technical prowess and knowledge he chose Verity to stand by his side. It was the young tech-priestess' idealism - some whispered naivete - he was interested in; a fervor to not only discover the light of the truth, but to uncover it and bring it to the galaxy at large, burning the darkness of ignorance and falsehood from the minds of humanity.
And so it was that Verity left Mars, in the company of the God-Emperor of Mankind, to embark on the Great Crusade.
She would never see her homeworld again.
