007.M42 – Agrellan, once a sprawling hive planet and the gateway to the Dovar System in the Eastern fringe of the Ultima Segmatum, lies in windswept ruin; a desolate monument to the pettiness of man.

In the twighlight years of M41, the Imperium failed to repel a T’au Empire expansionist fleet, despite a well-established standing planetary defence force, Imperial Navy Battlgroup, and elements from the White Scars Chapter of the Adeptus Astartes.

It was a rout, but rather than surrender Agrellan’s vast resources to the enemy and risk its population turning to the foul ideals of the “Greater Good”, a final spiteful blow was struck by the Mechanicus Priesthood with their world-ending technology: EXTERMINATUS.

Now, the planet lies in ruins. Hive spires that once stood 2 miles high are reduced to dust. Radioactive dust storms whip around the planet with enough strength to strip flesh from bone. Its once proud population, and the surviving T’au Empire forces have been reduced to feral scavenging in the tomb-like remains of the cities, or wandering the rad-baked deserts – survival their only remaining priority.

But underneath the ruin, something stirs. An ancient malice so deep in slumber, it took the destruction of a world to awaken it…