This expansion book for Warhammer: The Horus Heresy digs deep into the Garmon Cluster, a region of space that became the site of some of the largest pitched battles of the Age of Darkness. This book allows you to play out your own slice of this grand conflict, using an Onslaught Campaign system that links your games together as you fight through the Garmon Bulwark, as well as new Core Missions and narrative Apex Missions. You'll also find rules for Legiones Astartes Blackshields and Shattered Legions, new units for Solar Auxilia armies and rules for each Legion's attached Legiones Auxilia, as well as rules for notable characters from this tumultuous period.