Shadow on the Warp pt.1
In the first game, a group of rookie guardsmen are returning in a Rhino transport. Unfortunately, they break down close to an isolated settlement during a meteor storm. As the night progresses, it becomes obvious that something is not right in the settlement of Sanctuary. The inhabitants of the town seemed pious enough in their worship of the Emperor, living in the caldera of a extinct volcano that shelters them from the storm. They had come to live there approximately 70 years ago when their transport crashed, their leader Aldo explains. Unfortunately the radiation had left much of the population hairless and rendered them sterile. Suspicious, a number of the Guardsmen return to the Rhino. A middle-women, named Edith, accosts the Guardsmen, asking them if they've seen her little boy Tommy. Aldo and her husband quickly usher her away explaining that she lost her son some years ago.
The atmospheric disturbances caused by the meteor storm intensify, and the Guardsmen barely escape with their lives when a large meteor hits and incinerates the Rhino. Shaken, the Guardsmen see a strange pulse of light head skyward that seems to be energized by the storm itself. Meanwhile, other meteors continue to fall across Caernavon.
At the crash site, the meteor is a shape that seemed to be too regular for a normal meteorite. The intense heat prevented the guardsmen getting closer. As they returned to Sanctuary, they found the three bodies of a local predator, Razorwings. It looks like they have been shot out of the sky by some kind of corrosive agent.
Unnerved, the Guardsmen return to their makeshift accommodation in the town. They notice there seems to be a lot of furtive activity going on, and two of the Guardsmen are forced to open fire on two armed assailants outside the Guardsmen quarters. Aldo attempts to explain away the attack and appears terrified - apparently of the Imperial chapel, but then Edith appears once again overjoyed that she can hear her boy once again...
The chapel doors are flung open, and the Guardsmen discover that the whole town has been protecting their "children" - Purestrain Genestealers! Their secret discovered, the townsfolk scatter to the winds as the Genestealers close in.
A desperate fight for survival ensues as the three Genestealers attack, moving impossibly fast. Lasguns scorch carapaces and claws slice into flesh as both sides battle for the lives. With ammunition dwindling and Guardsman Enoch nearly becoming impregnated, Guardsman Cain desperately throws himself into hand-to-hand combat, pitting his sword against the razor-sharp claws of the last remaining alien horror. Hurled to the ground, Cain looks like he is fated to die when a lucky shot distracts the Xeno for a moment. He hurls himself upward slicing though the alien flesh and drenching himself in purple ichor. The Genestealer shudders and dies.
After burning the bodies, the Guardsmen are able to make contact and arrange a pickup. As they return to the capital, Callista city, they find the city in state of panic. The Adeptus Astra Telepathica have all been raving, talking of a terrible "Shadow in the Warp". Satellites on the edge of the system have picked up a large number of craft entering the system from the Dark Veil. Their configurations matching those on Imperial records: Xenos Tyrannicus. Tyranids. The Great Devourer has come. Another solar system begins to die...