Tallarn

Tallarn was once a green and pleasant world of temperate seas and fertile plains, home to a proud and numerous people. That Tallarn no longer exists. In a single act of treachery during the Horus Heresy, the traitor Iron Warriors bombarded the planet with life-eater virus, and in a matter of days the entire biosphere sloughed into rot, the seas turned to slime, and billions perished as their world died around them.

The handful of survivors endured only by sealing themselves into bunkers, mines, and the armoured hulls of tanks, sheltered from the toxic dust that now scoured the surface. What followed among the ruins became legend: the largest armoured engagement in the whole history of the Imperium, a war of thousands upon thousands of tanks fought across a poisoned desert where crews could never once open their hatches or step outside without dying.

That apocalyptic battle for a dead world raged for months, an inferno of tracks and shells and choking fumes, and though the traitors were ultimately denied their prize, the cost was almost beyond measure. Tallarn was left a rad-scarred desert planet, its glory drowned in dust, its people forever changed by the horror that had befallen them.

Yet Tallarn did not die entirely. Over the long centuries its survivors adapted to the endless deserts their world had become, and from them arose the Tallarn Desert Raiders, hardy soldiers of the Astra Militarum famed for masterful hit-and-run warfare across arid battlefields. The people of Tallarn carry the memory of their world's murder as a permanent grievance, and they fight with the quiet ferocity of a folk who have already survived the end of their world once and will not be caught unready again.