 Early in the Heresy, the Traitor Word Bearers Legion is tasked with organising and leading the invasion; they plan to use an immense, secretly commissioned warship, the , to spearhead the surprise attack.The vessel, commanded by Fleet Captain Zadkiel, launches from shipyards near Jupiter around the time of the events on Isstvan III (Book 3), and sets course for Macragge, Ultramar's capital world.Leading the cast of Loyalist protagonists is Cestus, Fleet Commander and Captain of the 7th Company of the Ultramarines.