Lectitio Divinitatus
The Lectitio Divinitatus (also Lectio Divinitatus) was a cult dedicated to the worship of the Emperor of Mankind during the Great Crusade and the Horus Heresy. Officially, the Emperor denounced religion or any claims of his divinity, but those who believed in the Emperor's godhood are of the opinion - as Titus Cassar once put it - that "only the truly divine deny their divinity".
The Lectitio Divinitatus is believed to be the precursor of the Imperial Cult, the basis of the modern Ecclesiarchy, but during the Great Crusade such cults were frowned upon by the Emperor and the Council of Terra, and most especially by the Astartes and those serving them. In the 63rd Expeditionary Fleet, commanded by Warmaster Horus himself, the cult was most prevalent. Horus took steps to try to extinguish the cult, as he perceived it as a threat to his power. The remembrancer Euphrati Keeler - who was attached to the 63rd - became a major figure, venerated as a prophet...a living saint of the Emperor. As a result, she was the target of Horus' assassins at some point before she escaped from the Vengeful Spirit. Even some Astartes - such as Nathaniel Garro, the Death Guard loyalist who led the Eisenstein escape - became part of the cult at one point.
At some point after the Emperor was interred in the Golden Throne, worshippers emerged from all across the Imperium, unifying the people until it became the official religion of the Imperium.
