The Octarius War

The Octarius War was born of a monstrous stratagem. Seeking to blunt two of the galaxy's deadliest threats against one another at a single stroke, agents of the Inquisition lured a splinter of the Tyranid Hive Fleet Leviathan into the very heart of the vast Ork empire of Octarius, gambling that the two ravenous alien horrors would grind each other into oblivion and spare the Imperium the labour.

The reasoning was seductive and utterly, catastrophically flawed. Orks grow ever stronger through struggle, evolving toward greater size and savagery with every battle they survive, while the Tyranids endlessly adapt their swarms to overcome any foe and devour the biomass of the fallen to birth new horrors. Rather than annihilating one another as hoped, the two species locked into a runaway cycle of escalation, each successive generation deadlier and more terrible than the last.

Octarius became a vast crucible in which perfect killers were forged without end. The greenskins swelled into a WAAAGH! of terrifying potency and cunning, while the hive fleet birthed monstrous new bio-forms tempered against the toughest and most warlike prey in the entire galaxy. What the Inquisition had hoped quietly to bury instead grew swiftly into a threat that dwarfed the original danger many times over. Neither ancient predator would ever relent, and the endless killing spread outward like a dark stain across the surrounding stars.

Worse still, the war could not be contained within its borders. The immense pressures of Octarius helped spill greenskin migrations and questing tyranid tendrils outward toward neighbouring systems, an object lesson written in blood about the folly of trusting to cleverness against the galaxy's oldest predators. The full account is told in the chronicle of the Octarius War.