Thrax is a Frontier World 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. Thrax is a Frontier World located on the Calixis-Scarus Warp route, its once tranquil, now war torn plains host to an array of weird fungus forests. Thrax has suffered greatly at the hands of Grimtoof Git-Slaver's forces, yet Duke Severus XIII has managed to cling tenuously to possession of the star system. The world of Thrax and several of its moons are densely populated, though technology is rarely more advanced than the black powder stage thanks to the system’s isolation. It is likely that Thrax was settled by human colonists long before the Age of the Imperium and never really integrated into the Emperor's domains, even over the course of the ten thousand years since the Great Crusade. Rather, Thrax's society has continued its lurching climb towards civilisation, the war on the Spinward Front setting it back millennia in one fell swoop.
The war has brought twofold suffering to the people of Thrax. On one hand, the advance of WAAAGH! Grimtoof has drawn numerous Ork warbands in search of slaves, and hundreds of thousands have been dragged off to serve in the Git-Slaver’s foundries. In response, Severus XIII has drawn equally heavily upon the world, forcing hundreds of thousands more to join the ranks of his own forces in the defence of the Severan Dominate. To make things worse still, the Imperium has launched a number of long-range strikes against Severus' bases on Thrax, though given the distance from the Imperium's lines, these attacks are invariably short-lived and highly focused, designed to cause strategic disruption to the Secessionists' operations.
The largest and most recent was in 815.M41, when the Imperial Guard launched a planetstrike against Thrax. Nine entire regiments were committed to an operation in the world's southern hemisphere, the intention being to gain a lodgement which could be supplied by orbital drop as needed. The landings were contested by a native force of roughly equal size, but the Imperial Guard should have been able to prevail given the time and space to bring their superior firepower to bear. Tragically, the landings coincided with a massive Ork slave raid and the landing force's orbital support was forced to withdraw in the face of the far larger enemy fleet. Cut off, the Guardsmen fought on, though under attack by two enemies. Exactly how many were slain is impossible to ascertain, though it is believed that the Orks captured thousands of troopers and dragged off to serve in Grimtoof's foundries. A force of regimental size is believed to have broken out, however, the survivors vanishing into the wastes where they continue to operate as guerrillas, launching punishing attacks on Severus' forces and living off of the alien land.
- Only War: Core Rulebook (RPG), pp. 346-348
- Only War: Enemies of the Imperium (RPG), pp. 8-31