Battle of Advex mors: Initial Assault, First Rangdan Xenocide. Explained | Warhammer 40k

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In this deep dive, we peer into the origins, legacy, and lasting mystery of The Battle of Advex-mors. A conflict that marked the beginning of humanity’s most catastrophic war against the Rangdan species. It stands as the opening act of the First Rangdan Xenocide, a campaign so devastating that the Imperium would later strike entire records from existence. In this archival reconstruction, we revisit the ruins of a war fought at the edge of comprehension, where the Emperor’s armies met an enemy that defied both biology and logic.

According to the earliest records, the Battle of Advex-mors began as a calculated strike by the Ist Legion later known as the Dark Angels led by Grandmaster Urian Vendraig. Their objective was the destruction of the Rangdan war-moon orbiting the primary world of Advex-mors Primus. The operation involved over fifty thousand Astartes and an armada of Imperial vessels. The battle’s progression reveals the Legion’s transformation from disciplined crusaders into a force driven by annihilation. Imperial forces employed precise orbital tactics, while the Rangda responded with adaptive, hive-like intelligence capable of synchronized warfare. Each engagement—from the siege of the hydrogen mines to the final confrontation between Vendraig and the Rangdan warmaster demonstrated the sheer scale of the xenocidal campaign. Though the Imperium triumphed, the cost was catastrophic: ten thousand Astartes lost, fifty warships destroyed, and the entire system rendered uninhabitable.

Administratum and Mechanicus records document the campaign as a logistical and technological crucible. The Adeptus Mechanicus analyzed the conflict in exhaustive detail, cataloguing energy fluctuations, weapon performance, and biological data from Rangdan remains. They concluded that the species merged organic and mechanical systems into one coherent network, each entity functioning as part of a larger sentient design. Mechanicum warships documented battles fought across multiple worlds, each characterized by coordinated extermination patterns and unprecedented levels of environmental manipulation. The Administratum later described the campaign as a model of efficient eradication—victory achieved through pure calculation. Yet even within these records, anomalies persisted: inconsistent data, repeating transmission patterns, and materials that appeared to alter when observed. To the Mechanicum, the war was a study in precision. To the Administratum, it was proof that precision alone could erode meaning.

From the Inquisition’s perspective, the war’s conclusion was anything but final. Centuries after the xenocide, Ordo Xenos expeditions to the Advex-mors system reported residual transmissions repeating at rhythmic intervals frequencies that mirrored human cardiac rhythm. Artifacts recovered from the site degraded only when examined, and pict-feeds displayed combat scenes inconsistent with known history. Classified Inquisitorial reports describe cognitive contamination among archivists, data corruption occurring in patterns too deliberate to be accidental, and dreams shared by those exposed to recovered fragments. Some within the Inquisition concluded that the Rangda achieved a form of distributed consciousness, persisting within data and memory long after their extinction. In the sealed archives of Terra, one phrase repeats across multiple reports: “The Rangda are gone. The war remains.”


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