The Adeptus Terra was sufficiently shaken by the news from the Ultima Segmentum to convene the High Lords of Terra. Their conclusion was rapid and succinct: the vast inroads of the Tyranids into the Imperium must be stopped at all costs, the Tyranid race must be investigated and, if possible, utterly exterminated. The Imperial Tarot predicted a time of coming darkness unmatched since the darkest hours of the Horus Heresy: the Devourer of Worlds grappled with the human galaxy and thus far it had shown only the first hints of its true strength. At the command of the High Lords the huge military juggernaut of the Imperium's armed forces turned its face to the Ultima Segmentum and readied itself for total war.

The forge worlds of the Adeptus Mechanicus produce tanks, weapons and war machines by tens of thousands. The ship yards at Bakka and Terra work night and day to build battlecruisers and warcraft to stem the tide of the Tyranid hive fleets. Millions of Imperial Guardsmen prepare to embark on a war for humanity's very survival. To the Imperium war is a religion, a crusade against the forces of darkness which wait in the shadows to enslave mankind. The Tyranids are the ultimate blasphemy, a race of creatures that brings not mere enslavement but utter extinction.

New and deadly Tyranid weapons and creatures are being reported all the time: long-ranged acidic projectiles which melt through steel like wax, creatures which attack with bolts of psychic energy or electro-static blasts, gigantic beasts as tall as Titans. The regularity of Tyranid attacks is increasing and no adequate defense has yet been discovered.

Several hundred large inhabited worlds have fallen to the Tyranids. Two entire Space Marine Chapters based on the Eastern Fringe, the Scythes of the Emperor and the Lamenters, have been all but destroyed with little more than a company of Space Marines surviving the Tyranid onslaught.

The fight has not been entirely in vain. In a number of systems Space Marines have boarded Tyranid ships while they were still dormant after exiting the warp. These boarding parties entered the pulsing vitals of the immense alien craft, gathering information about the Tyranids and destroying thousands of creatures while they lay frozen in hibernation. The information gathered by these brave Space Marines has proved vital to the Imperium' s search for a way to defeat the Tyranid menace.

The Techno Magi have concluded that the Tyranids originate outside the galaxy. Their voracious genetic structure and biological existence are different from even the most alien creatures of our own galaxy. Whereas human and other galactic organisms naturally diversify into distinct species over the course of millions of years, Tyranids evolve rapidly and constantly to meet the conscious needs of the entire race. The Tyranids are not one creature but a bewildering array of monstrosities created to perform specific functions. Hence Tyranids vary in size from the huge organic spacecraft of the hive fleets to tiny functionary creatures such as the beetle-sized scataphagoids which cleanse and recycle organic waste in the respiratory vents of the bin-ships.

The conscious mutability of the Tyranids means they have never needed to develop more conventional technologies like those used by Man. For example, much of the Tyranids' weaponry is created from symbiotic creatures which have been adapted and combined to fire voracious living shells or generate deadly energies. These artifacts have probably not even been consciously designed by the Tyranids, rather they design themselves in response to the requirements of the hive mind, genetically adapting to their tasks from the moment of inception. As time passes generations of the weapon symbiotes constantly change and evolve to become lighter, more efficient and deadlier against the Tyranid's foes.

The hive mind appears to require a constant influx of fresh genetic material and new DNA to create new creatures and adapt to different environments. The Adeptus Mechanicus postulate that the Tyranids exhausted their own galaxy and, perhaps, others of all life before crossing the interstellar void to seek fresh feeding grounds. With its billions of humans and countless other creatures the Imperium offers the Tyranids an inexhaustible stock of organic matter and genetic codes to invigorate the hive mind and enable it to manifest new forms. The Tyranids represent the nightmare pinnacle of evolution gone mad, a ravening super-predator of stellar dimensions which will make all other life forms extinct if it cannot be stopped.