Many of the Death Guard's Contemptor Dreadnoughts entered their long sarcophagus sleep during the Great Crusade's grinding early campaigns, veterans whose bodies had failed under exactly the kind of attritional warfare the Legion specialized in, and were later woken to find their Legion and their primarch transformed beyond recognition by Nurgle's plague. Some embraced the change as readily as their still-living brothers; others, sealed away from the worst of the corruption by their armored sarcophagi, retain fragments of the grim professionalism that once defined the Legion before Istvaan.
Regardless of how thoroughly Nurgle's gifts have touched the ancient inside, a Death Guard Contemptor fights with the same relentless, forward momentum the Legion has always favored, absorbing punishment that would destroy lesser walkers and continuing to advance long after the engagement should by any reasonable measure have ended. Their presence on the battlefield often marks the point where an enemy commander realizes that no amount of firepower will be sufficient to turn the Death Guard's advance back.