The Battle of Castobel
Tyranid History and Description
The Tyranid threat is a menace unlike any other faced by the Imperium, massive in scale and wholly alien in its nature and need to devour, not just mankind, but all life in the galaxy. The Tyranids are a vast swarm of predatory beasts driven and controlled by a single Hive Mind: one flesh, one will, and one biology, all designed to consume and absorb biomass on a monumental scale and focused solely on satiating a hunger without end. From the cold depths of intergalactic space they have come—the tendrils of the Great Devourer—an all destroying
swarm composed of billions of organisms, each one the agent of a great and immortal intelligence. They have left nothing but dead husks of former life-bearing worlds in their wake, and if the Imperium cannot stop them, all hope is lost.
Named for the doomed Explorator outpost on Tyran which fell before the onslaught of what would come to be named Hive Fleet Behemoth in 745.M41, the Tyranid threat has since ravaged hundreds if not thousands of star systems, principally in the Segmentum Ultima, like a vast and monstrous set of jaws biting down on the galactic plain, although no corner of the wide Imperium has so far proved beyond the reach of the fragmented tendrils of the onrushing nightmare tide. Indeed, the Genestealer, long an insidious threat that has troubled Mankind for millennia appears now to be a harbinger of the Tyranids, and the dim secrets of the ancient past hint at past threats, but never so widespread or potentially catastrophic as at present.
In battle, the Tyranids are a horror beyond comprehension, a monstrous tide of merciless claw, venom, and fang that cannot be bargained with, reasoned with, or surrendered to. It strikes with the relentless fury of a rabid beast, yet it is driven by a cold and alien intelligence that makes every component of the swarm—from lowly flesh-boring parasites to gargantuan war-creatures the size of a Battle Titan—far more dangerous than any mere animal could ever be. Carried through the void on immense living bioships, the seemingly numberless and inexhaustible hive fleets are attracted to worlds rich with life like a great ocean predator may be drawn to
blood in the water. They descend upon their prey-world, raining down poisonous spores that taint and pollute the atmosphere and unleashing murderous hunting creatures to slaughter any animal
life that might pose a threat to consumption. Depending on the particular fleet’s resources and size, other adaptive and mutating war-beasts and biologically created leader-creatures will also be unleashed to wage an unrelenting war of extermination on the world, a war that will only end in one of two ways: the defeat and purging of the Tyranid assault by the defenders, or the complete consumption and reduction of all living matter by the Hive Fleet, a dead world left in its wake.
Since the coming of the Tyranid menace, the Deathwatch and the Imperium’s armed forces have seen them rightly as a priority threat that must be met with and defeated, lest Mankind itself
some day perish in its jaws.