Consider, reader, the cruelty of the record: that somewhere on the northern edge of the Emperor’s expansion there dwelt a nation of Terra’s own children, more sophisticated in many arts than the Imperium that came to greet them, and that they were burned from the stars almost before the greater galaxy knew they had ever existed. The archives call them the Interex. The sagas remember them as a warning that went unheeded.
They knew of the Warp’s predators. They had a word for the corruption that pours from beyond — Kaos — and they had built a civilisation braced against it. And when Warmaster Horus, most beloved of the Emperor’s sons, extended his hand in friendship, they looked upon his Legion and quietly asked whether the Great Crusade itself might already be tainted.
Who the Interex Were
The Interex were humans, descended from Terra, who in the long night of Old Night had carved out a realm of their own among the stars. By the time the Luna Wolves of the 63rd Expedition encountered them during the Great Crusade, their civilisation is said to have spanned some thirty systems — a border nation, and yet one whose least frontier settlement could stand comparison with the conurbations of Imperial space.
The chronicles describe them as tall folk, near-identical to baseline humanity save for one deliberate refinement: great, bat-like ears grown to serve a language woven from music and sound. They still kept an evolved dialect of Terran speech, the archives note, but used it sparingly. Theirs was a culture that had concluded, through hard experience, that trenchant dependence on human traits — chief among them ordinary language — was itself an obstacle to mature dealings with other species.
The Kinebrach and the Long War
That hard experience had a name: the kinebrach. Squat, powerful beings clad in brown and gold, they were an advanced and ageing species who had held an interstellar civilisation across the local region for over fifteen thousand years — founding their multi-world dominion, the record states, before Terra had even entered its First Age of Technology, while humanity still crept beyond the Solar System in sub-light vessels.
When the Interex met them, the kinebrach were already fading. A territorial war broke out after first contact and ground on for a full century. Yet the reckoning that followed was not extermination but union. The envoy Diath Shehn told the Warmaster’s own audience chamber that this first great alien war had taught the Interex their place in the cosmos, and instilled in them certain values of compassion, understanding and empathy. From it grew the aria — their musical mode of contact, a tool fashioned for further dealings with non-human parties. The kinebrach entered Interex society and became, the archives say, an inextricable part of it.
Spiderland and the Xenos Wars
Nor were the kinebrach their only foe. The Interex met, fought and contained the Megarachnids, an aggressive alien breed that had begun savaging their frontier worlds — infesting, by one account, eight Interex systems before they were checked. Their prison-world for that menace was a planet they called Urisarach, a name said to function only with the proper harmonic accompaniment, which the Interex rendered as Spiderland.
It was this same murder-world, cast in the Imperial tongue simply as Murder, that the 63rd Expedition would find and fight across — a proving ground of blades and blood before the two human powers ever sat at a common table. From the first, then, the Imperials came to the Interex trailing violence.
Two Humanities Meet at Xenobia
When the embassy at last came to Xenobia Principis, the Interex received it with a great parade, culminating in the Imperials’ presentation to the senior royal officer of the world — a general commander named Jephta Naud. High civil officers walked in that party too, but the Interex had chosen, tellingly, to let a soldier oversee the meeting with soldiers.
The talks proceeded with meturge players lining the walls, their music underscoring every exchange. Yet beneath the courtesy lay suspicion. The Interex had, the archives whisper, been warned of the dangers of the Warp — some sources hold by the eldar, though this lies beyond the surest record — and they regarded the Great Crusade sceptically, fearing that the Imperials might already carry the taint of Kaos. They would not be made compliant. As Garviel Loken later judged it, they were too set in their ways, and their ways were set against the Imperium; there could be no accord without a war.
The Hall of Devices and the Stolen Anathame
Into this brittle peace crept treachery. Someone infiltrated the Hall of Devices — the Interex repository of artefacts and weapons — rigged the building to burn, and stole from it a kinebrach blade of terrible reputation: an anathame. The archives name the thief as First Chaplain Erebus of the Word Bearers, whose hand would shape so much of the coming ruin.
The theft shattered everything. To the Interex it confirmed their darkest fear — that the strangers were touched by corruption after all. Fighting erupted between the Astartes and the Interex host, and the Battle of Xenobia Principis raged until the Warmaster could be evacuated from the world. Whether the sabotage was meant to provoke exactly this, or to conceal the theft, the records do not finally settle; but the outcome served Chaos either way.
The Silence That Followed
Horus never forgave himself the failure. Long after, he brooded that he should have swayed that civilisation without a shot fired — that the Emperor would have done so — while his sons insisted no such path had ever existed. The archives note a grimmer legacy still: it was in the wake of the Luna Wolves’ inability to avoid war with the Interex that Horus, in counsel with Sanguinius, at last accepted the renaming of his Legion as the Sons of Horus. A dead civilisation stands, unmarked, at the root of that proud title.
The Interex themselves are believed to have been destroyed in the Imperial campaign that followed — after the Heresy broke open, no record speaks of them again. And the stolen blade did not vanish. That anathame, carried away in secret by Erebus, would be the very weapon that later struck down the Warmaster at Davin and set his soul upon the road to damnation. So the archives close the ledger with their bleakest irony: the one human realm that truly understood Chaos was annihilated, and the weapon torn from its hands became the instrument of Chaos’s greatest victory.