The Lorn V mission objective was to retrieve a long-lost Imperator Battle Titan, the Dominatus. Upon making planetfall, Sturnn was met by Eldar of the Ulthwé Craftworld and was forced to aid them, housing them in his base while he held off the Ork Waaagh! that attacked full force. Shortly after the battle, Farseer Taldeer told him of the Necrons, and that they would appear where the Titan had fallen.
Sturnn next received a communication from an Ultramarines Chaplain, Varnus, who had apparently been shot down deep in Chaos-infested territory. He reported that he was transporting crewmen for the Titan and required support. The Cadian 412th fought their way to his position, linked up with the Ultramarine force and ran the gauntlet of enemy forces between them and the Titan. However, they were beaten to the Titan by the Eldar.
Shortly after reaching the Titan, Taldeer and her forces set up a Soul Stone, a weapon apparently capable of annihilating the emergent Necrons. However, the Necrons arrived in numbers greater than expected and the Soul Stone was unable to eliminate them all. The only hope was for Taldeer to use her Bonesingers to encase the Titan's Machine Spirit in Wraithbone, so that it would be denied to the Necrons. With the aid of six Kasrkin squads sent forward by General Sturnn, the Necrons were eventually defeated, but with the loss of the Titan.
The Cadian 412th does not follow the standard enlistment of other Cadian regiments, adhering to its own structure. They do not use standard Command Squads, instead using command squads composed of commissars, Ministorum Priests and Sanctioned Psykers, but no Guardsmen.
In the novel Dawn of War: Tempest (Novel), General Sturnn reached the Titan first. He was visited by Space Marines from the Blood Ravens Chapter, who arrived in the company of Farseer Taldeer. Their goal was to activate the dormant Eldar Webway gate underneath the Titan. It also transpires that the Ultramarines who had come from orbit were actually Alpha Legion Chaos Space Marines in disguise.