Warhammer 40k - 2013 Advent Calender Short Story - Typhus: Herald of the Plague God by David Annandale

A world of perfect faith and matchless purity, Annunciation is one of the holiest planets in the Imperium. Of course, the higher the rise, the further there is to fall. This, Typhus knows well. As one who once fell from grace, he is determined to bring Annunciation to the same fate. And he is determined to do so alone. But what can one Chaos Space Marine do against a world of countless billions of souls?