In the closing years of the Forty-first millennium the Imperium was struck with the most devastating Black Crusade ever launched. Hundreds of worlds were drawn into the conflict, many of which were far removed from the main battleground of the conflict, faced attacks from the archenemy. One such incident was the Battle for Amatsu and the various battles leading up to it, in the ensuing conflict, which resulted in the deployment of several hundred Guard regiments and almost an entire Space Marine chapter.
The Battle for Amatsu at the time was deemed a critical conflict as the Amatsu system holds strategic importance, being located in a critical location for trade and as a port for Naval assets. However, at the time no one could imagine the scope of the campaign and the far-reaching affects that it would cost.
From Light in the Dark: The tale of the destruction of the 13th Black Crusade
The official history of the Amatsu Conflict notes many important details. However, as with most conflicts there is a dark side to the war. A side marked with deceit and betrayal. The records of this side of the conflict have been seals for all except those who carry the I of the Inquisition. In these sealed records is a story of faith, betrayal, loyalty, honor, courage, and deceit. It is a story of revenge and sacrifice, and yes, even a story of love. It is how the love of country, of friends, of family, and the love between two star-crossed lovers who stood together against the darkness, took a stand and stalled the advance of the foul worshipers of Chaos for now.
It is the closing years of the Forty-first millennium. For more than a hundred centuries the Emperor has sat immobile on the Golden Throne of Earth. He is the master of mankind by the will of the gods, and master of a million worlds by the might of his inexhaustible armies. All of this balances on a knife's edge. In the black heart of the Eye of Terror ancient enemies plot against the Imperium. Old grudges will be settled as Abaddon the Despolier plots to strike out against the Imperium once more. Seizing the moment a plot begins to weave itself as dark forces plot against the system of Amatsu.
In that system ten thousand years ago an ancient enemy was humiliated. Now they seek revenge for those ancient injuries. Millions will die, worlds will be shattered, but the wrath of Chaos will be felt throughout the galaxy.