- "Your offer to surrender has been received and rejected; we have not come to restore order or receive supplication, but to enact the Divine Emperor's judgement. Your loyalty has been weighed, measured and found wanting. Your fate has been writ by your own deeds. The time of judgement is at hand."
- — Murdering Sons multi-channel vox-broadcast, the Pacification of Mortikah V
The Mortikah Pacification is one the first known recorded engagements of the Murdering Sons Space Marine Chapter following their inception, which occurred during the dark era known as the Nova Terra Interregnum, a period of extreme unrest and civil strife, when the Imperium of Man was split in half, during the early-to-mid 35th Millennium. During this time, there were multiple foundings of Space Marine Chapters created to counteract the many outside threats to the unstable borders of the Imperium during this tumultuous period in Imperial history.
The Mortikah Pacification is not a campaign that Imperial history wants to commemorate. If it is remarkable for anything, it is for the depths of brutality reached in its prosecution. It is also not alone, however, but is merely one amongst many that the Murdering Sons would go on to prosecute during the so-called Retribution Crusade.
This Imperial campaign is notable for being a massive endeavour of genocide and terror against secessionist forces across the Segmentum Pacificus that would go down in Imperial annals, the likes of which had not been seen since the time of the Great Crusade. This particular campaign would cement the Murdering Sons' mark of horror as well as their savage reputation. Instead of a great victory, this particularly brutal campaign instead reads more like a condemnation. The Mortikah System lay closest to the borders of the Segmentum Solar, and so, this string of populous worlds was the first to feel the wrath of this ferocious Chapter.
An ancient stele mounted within the Church of St. Pancratius recognises the services of the Murdering Sons for their actions against the heretic and the apostate, putting down the insurrections and rebellions that were rife throughout the populated the worlds of the Mortikah System in the 35th Millennium. This artefact praises the Chapter and credits them for having "brought the Emperor's retribution.." to "cleanse the corrupted with bolter and blade." On numerous worlds throughout the Mortikah System there are scattered and veiled references to "a dire threat that arose from the east..." and of "sable-clad" Space Marines who wore memento mori upon their battle-plate.
Those incomplete records which have been uncovered from various fragmentary Imperial data-vaults suggest that this Chapter was none other than the so-called 'Homicidialis Filios', or in the Low Gothic tongue, the Murdering Sons. Much of the extant evidence relating to the Mortikah campaign has been censored or purposely destroyed, but there are consistent reports which describe the nature of the horrific acts carried out by these avenging 'Angels of Death' upon the worlds of the Mortikah System, and how the Murdering Sons swept away scores of worlds in a wave of violence unheard of, slaughtering whole sectors in their wake.