As the crusade reaches its apex, Lord Solar Macharius is drawn by a prophecy to the world of Demetrius in search of an ancient artefact - the Fist of Demetrius. Rumours and legends abound of the artefact's providence as a weapon of a primarch, the lords of the Horus Heresy. With it, Macharius believes his success and victory is assured but others crave this potent weapon, and the dark eldar will do anything to obtain it.