Tallarn

Tallarn is a former Imperial agri-world reduced to desert by Iron Warriors virus bombs and the setting of the largest armoured battle in human history. Its ruin dates to the opening years of the Horus Heresy, when Perturabo’s IV Legion turned from the primarch’s wider siege campaigns to strip the world of its fertile land and break its Army garrison in a war fought almost entirely by tank crews.

The Iron Warriors’ virus bombardment killed the bulk of Tallarn’s population within hours and converted its farmland into open desert, but the surviving armoured regiments refused to surrender, drawing Warsmiths Kroeger and Kydomor Forrix into a grinding campaign of manoeuvre across the dunes rather than a swift occupation. The desert surface was never the true prize: beneath the sand lay a warp gate bound to the Cursus of Alganar, an Eldar construct the Iron Warriors sought to uncover, which turned the tank battles above into cover for a deeper contest over what the gate might open.

Survivors who fled into the tunnel networks beneath the desert endured as scattered tribes, and their descendants later furnished the Astra Militarum’s Tallarn Desert Raiders, a regiment still shaped by the guerrilla armoured warfare their ancestors waged against the Iron Warriors. Long after the Heresy-era fighting ended, the Eldar of Biel-Tan returned to Tallarn to re-bury the Cursus of Alganar a second time, a separate and much later episode that has no recorded connection to Perturabo’s campaign beyond the artefact itself. The two threads, Iron Warriors against Tallarn armour, and Biel-Tan’s subsequent action at the Cursus, mark distinct moments in the same world’s long entanglement with the gate beneath its sands.