Following the actions of Captain Ventanus and the remaining Imperials on Calth, eventually they were rescued by the Ultramarines. The "Saviour of Calth" became one of Primarch Roboute Guilliman's closest advisers. Led by their erstwhile Captain, the 4th Company, known in some circles as the Troublesome Fourth, was a company known for its daredevil actions, heroic follies and the personal bravery of its individual warriors. They would become instrumental in helping to play out the strategies and military tactics devised by Primarch Guilliman in simulated battles -- the results, which would help lay the foundation of his greatest work, his Magnum Opus, the undertaking for which he would be forever remembered -- the Codex Astartes. Decades of accumulated wisdom, each chapter and verse a fragm