The Imperium is by far the greatest single human power in known space. Its interests are vast, and impact every facet of human existence. Backed by a highly trained and well equipped Starforce, the Imperium maintains the dominant role in interstellar trade and commerce, and all major trade routes and sales of advanced technology are regulated by the Imperium. It is the backbone of the Starcaste system, and the strength about which the Starguild is united.

"The laser of an Imperial Starmarine is the direct extension of Imperial foreign policy"
―Mark Presserton, Former apprentice member of the Starguild Council.[src]

The Imperium was involved in a power struggle with RMBK. A few weeks before the Spectral invasion, the Imperium had responded to RMBK's refusal to divulge its secrets by sending the 7th Imperial Guard Strike Battalion, one of the most powerful forces in known space, to Rhand.

When the invasion came, Imperial forces efficiently and quickly dispersed by Squad to maximize their chances of surviving the anticipated bombardment. Many units used the ORCA to reach remote regions, far from likely ground targets. This dispersion protected them from both the bombardment and infection by the Spectral viral attack. Imperial forces came out of the invasion largely intact, but somewhat scattered.

Following the destruction of the Spectral ship, Imperial forces began to regroup. As this maneuver was completed, the various command units rallied with the Imperial Guard Strike Battalion to lay out plans for an immediate Imperial conquest of Rhand. The Imperium blamed Trident for the sabotage of the deep space tracking system preceding the invasion, and felt the invading spacecraft might even have been a Trident vessel. This analysis was not completely unreasonable, as little information had been gathered concerning the Spectral attack. At the time no Spectral forces had been seen, except for unconfirmed radio reports of alien ground forces operating in the southern hemisphere. The reports from the south were dismissed as part of the overall Trident deception plan. The Imperium was convinced that Trident forces were responsible for the attack, and planned to retaliate.

Shortly after the Imperial command units gathered, they were attacked and almost totally destroyed. A few Imperial troops escaped, but the Imperial command elements were lost. Personnel who escaped have given conflicting and unclear accounts of the brief action. Some claim that they were hit by heavy Power Armor, some say it was unarmored fanatics, while a few swear they saw Spectrals or even Dragoncrests.

The end result of this defeat is the inability of Imperial forces to rally. Their command structure has been shattered and units in the field are now striking out on their own. After two months, many feel no reinforcements are coming and most are looking out for themselves. The strict military code and structure they embraced before the invasion has now generally been discarded, and the Imperial military now resembles common merce-nary units. They do not like the idea of rejoining higher command and are using their military training, organization, equipment, and new-found freedom to set themselves up as conquerors of the Apocalypse. A few units are still trying to rally and assemble a cohesive force, but those are in the minority. Until there is again a strong force operating in Rhand which can establish discipline, these units are likely to lead lives of conquest and plunder.