Karacallia is a heavily-populated star system controlled by the Severan Dominate and located in the Periphery Sub-sector of the Calixis Sector. It is currently a front line in the conflict consuming the Spinward Front. The Karacallia System contains an unusually high number of gas giants, many of which harbour resources of use to the Adeptus Mechanicus in the construction of Warp-Drives. Though logged, the system's resources have never been properly exploited, its location some distance from the nearest Forge World, making it a perilous undertaking and the war making it all but impossible. The population of the Karacallia System is scattered across three-dozen and more satellites of the various gas giants and represents the descendants of a first wave of Imperial colonists dispatched there five standard centuries ago to populate the system and thus provide the raw manpower needed to exploit its resources in future generations. But the scheme never reached fruition and, though the population has thrived numerically, it has suffered greatly from its isolation. Thus it was not difficult for Severus to stoke the fires of rebellion on Karacallia, and the densely populated worlds are ripe recruiting grounds for the Dominates.
Of the dozens of populated worlds in the Karacallia System, not one is untouched by war. The Imperium has launched over thirty separate assaults since the beginning of the war and the Orks at least the same number. To date, none of these assaults has dislodged Duke Severus XIII's forces, which fight with almost unholy zeal. Numerous Imperial Guard regiments have been committed to the system and, while substantial gains have been made in the past, most have been at the expense of losses elsewhere. While one satellite might be taken, another will fall, and so war ebbs and flows across the war-torn moons and planetoids. The surfaces of the worlds are cratered, corpse- and debris-strewn wastelands, poisoned by the lethal gases Severus XIII's forces have unleashed and scoured lifeless by the weapons of the Imperium. The war there has been likened to an "island-hopping" campaign, with forces fighting for possession of the countless satellites and planetoids. It is rare for any single world to be held by one side for more than a few solar months before the enemy dislodges it, but still the war grinds ever on, the system's location along the Calixis-Scarus Warp conduit making its possession vital.
- Only War: Core Rulebook (RPG), pp. 346-348
- Only War: Enemies of the Imperium (RPG), pp. 8-31