8th Black Crusade
As the Eighth Black Crusade raged across the stars, the Black Legion struck out from the Eye of Terror in every direction. At first the Imperium could only guess at the Traitor Legion's plans, as some raids accounted for entire settlements where others only seemed to cause limited carnage by the horrific standards of the Black Legion. On the moons of Teekus, eight of the twenty crater cities were peeled open to the void, their inhabitants freezing in place while the others remained untouched. The chartist pilgrim vessel the Divine Path was waylaid en route and nine-hundred and ninety-nine of its passengers were murdered in ascending order of the pilgrim tokens they carried. The rest were left to weep over the fallen.
In what later became known as the Skullgather, tens of thousands were killed across the Segmentum Obscurus in a variety of ways and in specific numbers, their corpses left in ritualistic patterns. It was part of a plot to appease Tzeentch, the numbers and patterns creating a mathematical equation of terrible and profane perfection. While Imperial forces pursued the Black Legion, trying to bring them to battle, the Inquisition attempted to break the cipher, driving hundreds of adepts insane in the process.
Finally, on the forge world of Rithcarn, the Traitors instigated a massive uprising of the mutant workers, plunging the world into chaos and ruin. In the confusion, the Black Legion sacrificed the council of Tech-Magi in the gears of their own manufactorums; with their destruction, the complex sequence of death was complete and Tzeentch greatly pleased.
- 1: Black Legion - A Codex: Chaos Space Marines Supplement (E-Book) pg.36-37