Belisarius Cawl - 13th Black Crusade: At the time of the 13th Black Crusade in 999.M41, Cawl, in command of the Ark Mechanicus Iron Revenant and a large Mechanicus fleet including Skitarii troops and powerful Kataphron Battle Servitors, was guided by the Aeldari Harlequin Shadowseer Sylandri Veilwalker to the world of Eriad VI, a former Imperial Navy base which had been abandoned during the 4th Black Crusade in the 32nd Millennium. Unknown to the Imperials, Eriad VI had also been a Necron Tomb World.After battling Orks who had been drawn to combat on the empty world with the powerful Mechanicus fleet, he recovered an ancient Necron artefact. He also learned more about the nature of the Cadian Pylons originally built by the Necrons that were tasked with restraining the eruptions of the Immaterium -- especially the Eye of Terror -- into realspace.Cawl uneasily accepted Veilwalker's enigmatic instructions to make his way to Cadia, already under siege by Abaddon the Despoiler's massed forces of Chaos, where his timely arrival provided desperately needed reinforcements for Lord Castellan Ursarkar E. Creed's embattled Imperial forces.While on Cadia, Cawl began his investigation of the local xenos pylons with the knowledge recovered from Eriad VI. During his investigation, the Necron Overlord Trazyn the Infinite, who had decided to intervene to aid Humanity against their mutual enemy in the Warp, made his presence known.Though wary of the Necron's motivations, Cawl's fascination with the highly advanced Necron technology of the pylons overcame his hostility to xenos and he accepted the Necron's aid.With Trazyn's knowledge, Cawl was able to determine how to use the pylons to cut off the local area of space-time from contact with the Immaterium. As the ground battle between the Despoiler's invaders and Ursarkar E. Creed's defenders reached its climax, Cawl activated the pylons.The Necron technology operated precisely as had been expected, cutting off Cadia from the Warp, banishing the daemons of Chaos, actually shrinking the Eye of Terror and giving Cadia's defenders a chance for yet another unlikely victory.Unfortunately, the Despoiler would not be denied the prize he had sought for millennia so easily. Foreseeing the need for a fail-safe, Abaddon had the damaged bulk of the Blackstone Fortress Will of Eternity, its systems disabled by an assault from the Imperial Fists' star fort Phalanx, hurled from orbit as an artificial meteor into the surface of Cadia. The massive kinetic strike destroyed what remained of the world's defences, ensuring its envelopment by the now rapidly-expanding Eye of Terror.Lord Castellan Creed ordered an evacuation of the dying world, and the Imperial survivors of Cadia -- led by Cawl, Saint Celestine, Inquisitor Katarinya Greyfax and Marshal Marius Amalrich of the Black Templars -- now calling themselves the Celestinian Crusade -- used every voidship at their disposal, including the Iron Revenant, to ferry the three million survivors off Cadia. Unable to enter the Warp because of the roiling instability of the Immaterium near the Cadian Gate, the Imperial fleet was forced to flee through the Cadia System at sub-light speed, and the Chaos warfleets gave chase.The largest and most powerful remaining Imperial capital ship, Cawl's Iron Revenant, heroically sacrificed itself in battle against Abaddon's flagship the Vengeful Spirit so that the Celestinian Crusade could escape to Klaisus, the nearby ice moon of the world of Kasr Holn.The Iron Revenant's loss was not in vain, for the surviving Celestinians were rescued from Chaos attacks and the unforgiving arctic environment at the last by the arrival of the Ynnari through Klaisus' hidden Webway gate. Though his flagship was lost, Belisarius Cawl had rescued its most precious cargo -- the Armour of Fate, key to the resurrection of the Primarch Roboute Guilliman.