Age of Darkness

After the betrayal at Isstvan, Horus begins his campaign against the Emperor, a galaxy-wide war that can lead only to Terra. But the road to the final confrontation between father and son is a long one seven years filled with secrecy and silence, plans and foundations being formed across distant stars. An unknown history is about to be unveiled as light is shed on the darkest years of the Horus Heresy, and revelations will surface that will shake the Imperium to its very foundation... Age of Darkness enters a new chapter of the epic Horus Heresy story, and features stories from some of the Black Library's best-known authors, including Dan Abnett, Graham McNeill, James Swallow and Aaron-Dembski Bowden.

Read it because
The first phase of the over, and the Age of Darkness begins. These tales show the state of the galaxy as war engulfs it and lay hints to what is to come.

The eBook edition includes integrated illustrations of characters and events from the story, and an afterword that places the story in context within the series.