The Insurgency is a Black Crusade campaign set in the Periphery Sub-Sector. Serving the Great Host of the Bloody Born, the Players have proven themselves in an prior engagement. This has led to them being chosen by Warlord Skrallos himself to participate in an important campaign.
The secession of the Severan Dominate has forced the Imperium to move military assets from the greater Calixis Sector, the Koronus Expanse, and even the Scarus Sector. This means that these sectors are now vulnerable. As long as the Severan Dominate opposes the Imperium, then Skrallos and his warband can easily move into those sectors.
As such, Skrallos has set his sights on the planet of Tethys, where the Dominate are desperately fending off an Imperial advance. The Players, disguised as either military advisers or mercenaries, are to aid the Severan defense. Their ultimate mission is to prolong this defense, and destroy enough Imperial assets, where the Imperium will direct more and more assets into the campaign.