Remembrancer Ignace Karkasy reports back on the meeting to his sponsor, Captain Garviel Loken, revealing that Erebus manipulated Horus into becoming enraged at Temba and must have an ulterior motive for wanting Horus to go to the moon. Enraged, Horus orders an immediate attack on the moon. A War Council is convened on Davin's surface where Erebus reveals his reason for summoning the Warmaster to the planet: its planetary governor, Eugen Temba, has turned against the Imperium and betrayed Horus after taking his forces to the planet's moon to put down a rebellion by the Davinite tribes there.
They are joined by Petronella Vivar, scion of a Terran noble house who becomes Horus's documentarist. The 63rd Expeditionary Fleet under the command of Warmaster Horus Lupercal rendezvous with elements of the Word Bearers Legion under First Chaplain Erebus on the planet Davin, which their Legions jointly brought into compliance six decades ago. With all the temptations that Chaos has to offer, can the weakened Horus resist? Horus is still battling against the jealousy and resentment of his brother primarchs and, when he is injured in combat on the planet Davin, he must also battle his inner daemons. Yet all is not well in the armies of the Imperium. The Emperor of mankind has handed the reins of command to his favoured son, the Warmaster Horus. The Great Crusade that has taken humanity into the stars continues.