Sulian Genocides

The Sulian Genocides was a horrific campaign of genocide carried out against the Corpse Kings own sub-sector of responsibility. Revealing their perfidy, the Renegade Chapter proceeded to assaulted the half dozen planets within the sub-sector, laying waste to whole cities and slaughtering any and all survivors, leaving ravaged worlds of blood and ash. The slaughter was only temporarily slaughtered when the sub-sector was attacked by a large Black Legion warband and the near simultaneous arrival an Astra Militarum regiment. Fighting alongside their fellow Imperial 'allies', the Corpse Kings and the mortal troopers made short work of the Black Legion warband. After this problem was dealt with, the Corpse Kings then turned upon their weakened allies, and cut them down with bolter and blade.

History
Having carefully watched over the Sulian Sub-Sector for years, the Corpse Kings deploy the 6 Battle Companies alongside their Scout Company to the 6 planets of the sub-sector with the intention of killing each and every mortal inhabiting the sub-sector. Finding the PDF of each planet to be lackluster, the Corpse Kings began cutting a bloody swathe through enemy lines with zero hesitation until the Chaos Space Marines of the Black Legion and the Imperial Guard forces they were fleeing from arrived on the sub-sector. Albeit reluctantly, the Corpse Kings agreed to cover up their renegade status and introduced themselves to the Imperial Guardsmen as a proud and noble Ultramarines successor who had been sent to the sub-sector to root out heresy.

Siding with the Imperial Guardsmen to deal with the Black Legionnaires, the Corpse Kings fired upon the Imperial Guardsmen the moment they smelled weakness. Cutting through the already weakened and shocked Guardsmen easily, Corpse Kings left the sub-sector, satisfied with the slaughter they carried out. It is yet unknown how many mortals they killed, but many are certain that the numbers are way higher than the number of people the Nurglite warband known as The Purge managed to kill during the Vaxhallian Genocide.