Although not directly relevant for the campaign, at least not for the time being, momentous events are taking place elsewhere in the galaxy:

To the galactic east the 13th Dark Crusade is just about ready to launch under Abaddon the Despoiler's command. In the meantime individual Chaos warbands raid far and away from the Cadian Gate, reaching as far as Calixis and beyond. To the Imperium as a whole it is more of a nuisance, but for those unfortunate enough to be caught in the raids its bad enough. Help from Sector or Segmentum assets is also less likely than normal, seeing as how much of the resources of Segmentum Obscurus are been drained away by the preparation for a major war effort.

Far to the galactic south and east another impossible threat looms, that of the Tyranids. Though some Ordo Xenos Inquisitors theorized that Tyranid infiltrators have long been a presence in the galaxy, it was the appearance of Hive Fleet Behemoth two-and-a-half centuries ago that got the Imperium's attention. Only the desperate resistance led by the Ultramarines, their vassal Chapters and the greater part of Battlefleet Tempestus was finally able to defeat Behemoth. Although scattered remnants of the Hive Fleet continued to plague the far south-eastern reaches of human space they did so in a near-mindless fashion, and the Imperium considered the Tyranids defeated, and down-classified them as a lesser threat.

That changed with the arrival of Hive Fleet Kraken on the extreme eastern fringe of the galaxy, far beyond the blessed light of the Astronomicon. As Hive Fleet Kraken continued its advance it came into contact with scores of lesser species, but it was not until it infringed upn Tau and Imperial space that it ran into real resistance; but that time it had become a bloated many-pronged flee quite unlike the more concentrated Behemoth. Hive Fleet Kraken was eventually halted in 993.M41 at Ichar IV, Iyanden Craftworld, and the D'yanoi Sept (not that the Imperium has made a habit of giving xenos credit, but the facts are logged with the Ordo Xenos). The surviving elements of Kraken continued to be classified as high-threat aggressors, preying upon isolated or ill-protected worlds, but once again the Imperium considered the overall Tyranid menace ended – perhaps because the alternative was too horrible to contemplate...

But now astropaths report a dark and dread presence approaching the Imperium, far greater than anything sensed before. Approaching from below the galactic plane it bores straight into the heart of Segmentum Tempestus, and the Imperial Tarot spells only death and doom for the worlds in its path...Hive Fleet Leviathan is about to wash over Segmentum Tempestus, and this time the Tyranids will not be denied!

Compared to the threats of Chaos Marauders and Tyranid Hive Fleets everything pales...save the heresies and treacheries begotten by man against his fellow men. Indeed, what could better illustrate this than the rumors of vile heresy that have begun drifting up from the Galactic South? All sorts of evil is being whispers, but a certain dark core can be gleaned by combining the oft-contradictory lies st forth by foreigners of little faith and no moral fiber; that somewhere in Segmentum Tempestus a traitor walk the land, claiming to be the Emperor Reborn! Yes, on the eve of battle man will betray his fellows – who needs enemies who has such neighbors and friends...