Although Legions such as the Iron Warriors are well-known for their mastery of Daemon Engines, the hosts of the Grandfather are not without their own special panache for enslaving unwitting machine spirits to their cause. The underlying motivations of their code undergo unholy transformation under the ministrations of virulent electronic viruses while their carapaces and inner workings are assaulted by the Ferric Blight.
These esoteric blessings of Nurgle are easily transmitted from one machine to the next and soon an entire phalanx of rusted, grinding, choking, and spewing engines encroaches on the enemy positions. Although the vehicles making up a Ferric Blighthost appear structurally compromised, very little remains of the original workings of their filthy middens. The glorious gifts of the Grandfather have made them capable of implacable, grinding assaults which can break the enemy lines, opening up opportunities for the infantry following close behind.