The moon of Kau’Rela sits on the Eastern fringe of the Ultima Segmentum of the Milky Way galaxy. Though ostensibly claimed by the Imperium of Man, no known settlement has been documented by humans. As preparation for their Fourth Sphere expansion, the Tau Empire established a set of forward colonies on the dusty moon to begin terraforming it for further habitation. Communication with the colony was lost, with only a single transmission picked up by the nearest Tau fleet: “Y’he” or Tyranids.
Several dispatches and a distress beacon were, however, intercepted by an Ad Mech probe that had previously drifted off course and been thought lost. The frequency was an older code, but it checked out. The heretical information was passed along to several sources within the Imperium, including a ranking member of the Inquisition who had just been called away and the closest Adeptus Astartes, in this case a fraction of the Dark Angels passing through. Analysis of the moon indicated that sabotage of the heretical Tau terraforming devices by one or the other of the two xenos threats had destabilized the planet core and triggered a rise in geothermal and volcanic activity. Though some notable biomass remains, much of the planet may be categorized as ash wastes. Company Master Jevriel of the Dark Angels and his men prepare to make landfall.