Lectitio Divinitatus - History: Those who followed the teachings of the Lectitio Divinitatus eventually became an underground religious cult of the same name across Imperial space by the end of the 30th Millennium. This cult is believed by current Imperial scholars to be the precursor of the Temple of the Saviour Emperor and the Imperial Cult, the unreformed antecedents of the present-day Ecclesiarchy and the state religion fervently practiced in the 41st Millennium by trillions of Human beings across the galaxy.During the Great Crusade, such cults of Emperor-worship were deeply frowned upon and condemned by the Emperor and the Council of Terra, and most especially by the Legiones Astartes and those serving them, as a violation of the secular Imperial Truth which held that only reason and science offered a guide to understanding the universe.The Emperor denied His divinity outright, but those who believed most firmly in the Emperor's divinity were of the opinion -- as the officer of the Emperor Titan Dies Irae, Titus Cassar, once put it -- that "only the truly divine deny their divinity."In the 63rd Expeditionary Fleet of the Great Crusade, commanded by the Warmaster Horus himself, the Lectitio Divinitatus cult was very prevalent, though hidden, among a large minority of the mortal men and women serving in the fleet. Horus took steps to try to extinguish the cult, as he perceived it as a threat to his own power, particularly after he embraced the service of Chaos following his healing at the Temple of the Serpent Lodge on the Feral World of Davin.The Remembrancer Euphrati Keeler -- who was attached to the 63rd Expeditionary Fleet -- became a major figure of the early Lectitio Divinitatus cult and was canonised as one of the first Imperial Saints after the establishment of the Ecclesiarchy in the 32nd Millennium.Keeler was venerated as a prophet and Living Saint of the Emperor even during her own lifetime. As a result, she was the target of Horus' assassins at some point before she escaped from his flagship, the Vengeful Spirit, at the bidding of Captain Garviel Loken and with the aid of the Luna Wolves Captain Iacton Qruze.Even some Astartes -- such as Battle-Captain Nathaniel Garro, the Death Guard Loyalist who led the escape of the Loyalist frigate Eisenstein from the massacres on the world of Isstvan III in the Isstvan System and was the first of the Knights-Errant of Malcador the Sigillite -- later became part of the cult, largely because of Keeler's influence and their own experiences with how faith in the Emperor could be used as a weapon against the supernatural horrors of the Warp.At some point after the Emperor was interred in the Golden Throne following the end of the Horus Heresy in the early 31st Millennium, billions of worshippers emerged from all across the Imperium.This faith unified the Imperial people against the myriad threats and horrors of the galaxy in their common belief that "faith in the Emperor protects" until the cult of the Lectitio Divinitatus became recognised by the High Lords of Terra as the official state religion of the Imperium in the mid-32nd Millennium in the form of the Temple of the Saviour Emperor.As such, the faith in the God-Emperor inspired by the Lectitio Divinitatus became the foundation of the Imperial Cult administered by the priesthood of the Adeptus Ministorum.