- "From the fires of Betrayal unto the blood of revenge we bring the name of Lorgar, the Bearer of the Word, the favored Son of Chaos, all praise be given to him. From those that would not heed we offer praise to those who do, that they might turn their gaze our way and gift us with the Boon of Pain, to turn the Galaxy red with the blood, and feed the hunger of the Gods."
- — Excerpt from the three hundred and forty-first epistle, Book of Lorgar
The Book of Lorgar was said to be a tome penned by the Primarch of the Word Bearers Space Marine Legion, Lorgar himself, following his dealings with the old priesthoods of the Dark Gods and their corrupt masters.
The tome was written following Lorgar's introduction to Chaos by his First Chaplain Erebus after the Word Bearers helped the Luna Wolves bring the world of Davin into Imperial Compliance during the Great Crusade. The Book of Lorgar was bound in the flayed skin of Loyalist Legionaries who had died during the Istvaan III Atrocity, and though Lorgar considered the gesture decadent, he believed the symbolism in such things was important to those who might become faithful servants of the Dark Gods.
It is rumoured that Lorgar wrote another version of the Book of Lorgar as well. This is the version he shared with his brother Primarchs. This was his writing in its purest form, his true philosophy down in ink. It was not the teachings of Erebus nor Kor Phaeron, which were the mere recitals or dictations of the Chaos Gods themselves.
This other version was the true Book of Lorgar, the scripture that was penned to inform the Word Bearers Legion about the truths of Creation for millennia to come. Lorgar called it the Testamentum Veritas (in Low Gothic, "Testament of Truth"). During the Horus Heresy it was known that Argel Tal, the first of the elite Word Bearers Possessed Chaos Space Marines known as the Gal Vorbak and Lorgar's most favoured son, was gifted a copy of this version of his Primarch's true testament in a great skinbound tome secured to his waist by a bronze chain.
The Astartes of Lorgar's XVIIth Legion, the Word Bearers, held this text as sacred, in spite of the concern this caused for others, including the Emperor of Mankind, who believed that all human religion and mysticism must be suppressed by the pure scientific rationalism of the Imperial Truth.
The Word Bearers' First Chaplain Erebus, who later became one of the Legion's Dark Apostles after the start of the Heresy, bore tattoos upon his shaven scalp said to depict long passages from the book, that he might terrify his foes with the strength of his conviction in Chaos.
Whilst attempting to decode these tattoos and text from the book itself, Imperial Iterator Kyril Sindermann inadvertently summoned a Lesser Daemon from the Warp which destroyed many of the Librarium archives aboard the Warmaster Horus' flagship the Vengeful Spirit before it was banished to the Immaterium once more through a miracle of faith performed by the future Imperial Saint Euphrati Keeler.
- False Gods (Novel) by Graham McNeill
- Betrayer (Novel) by Aaaron Dembski-Bowden, pp. 77-78, 124
- Dark Apostle (Novel) by Anthony Reynolds