During the invasion, the Castellan's forces, alongside the Knights of House Mortan led by Sir Dirkwald, defended Ghreddask against the forces of the Warpsmith Etrogar. The Warpsmith had attacked the Hive World, using the parasitic Soul Harvester Scarax Krond, whose hab-block size tentacles burrowed themselves beneath Ghreddask's surface. This had allowed the Soul Harvester to feed off the world, to indefinitely create Daemon Engines as well as easily disgorge Etrogar's Iron Warriors forces. As long as it was operational, the Imperium would be unable to defeat the Warpsmith and this caused Dramos to order the Scarax Krond to be invaded. Then as his Templars and Mortan's Knights fought the Iron Warriors, the Castellan's Command Squad fought its way to the Soul Harvester's heart. There, in an act of self-sacrifice that would mark their names in the honour-scrolls of their Chapter, Dramos and his Command Squad detonated a cyclonic charge. Though the resulting explosion did not destroy the Scarax Krond, it heavily damaged the Soul Harvester and gave the surviving Imperial forces time to regroup.