The Great Malagantine Purge was an Imperial military operation carried out in the years 770-791.M38 by 5 Space Marine Chapters collectively termed the Manus Irae who unleashed the Emperor of Mankind's wrath upon the heretical Malagant Sector in the Segmentum Tempestus. The details of this operation have been kept secret from the Imperial Adepta, including the Inquisition, with the records of the campaign sealed deep within the Celarno Vaults on Terra. What is recorded in fragmentary Imperial records is that the Manus Irae were charged by the High Lords of Terra of that era to "spare none and set a bloody, fearful example to the realm of Mankind." The death toll unleashed by the Manus Irae during the course of this 21-year long campaign is believed to have been enormous and to have cost hundreds of billions of lives. Whole worlds were put to the sword by the Astartes or were wiped clean of all life by Exterminatus orders that unleashed a hideous, flesh-dissolving virus upon their inhabitants. In recognition of their successful participation in this campaign, the Fire Hawks Chapter was granted the Feudal World of Costeau XI as their demesne by the High Lords. However, due to their willingness to carry out such merciless exterminations of civilian populations whose guilt was not clear, the Fire Hawks would be shunned thereafter by many of their fellow Astartes Chapters.
The Black Fragments of Cardinal Bloch the Reviled, one of the few remaining heretical sources which contain information concerning the Purge of Malagant, explains that the Manus Irae consisted of 5 Chapters, but listed only three by name, including the Fire Hawks, Silver Skulls and the Charnel Guard.
- Imperial Armour Volume 9 - The Badab War - Part One, pp. 68-69