Battle of Calth - Desperate Hope: The Grand Cruiser Antrodamicus survived its unpowered fall through Calth's atmosphere from orbit largely intact, but its blazing bulk demolished a large swathe of the once teeming city of Kalkas Fortalice, clearing a patch two and a half kilometres wide. Meteoric debris continued to rain down from the sky all around it, bombarding the city and the surrounding landscape. Fortunately, Magos Tawren managed to flee the destruction of the Watchtower before the large vessel struck the planet's surface. Little information about what had occurred in orbit was available to the Loyalist survivors on the planet's surface.They knew that there had been some major incident in orbit that was raining destruction down on Calth, but whether it was an accident or an attack remained unclear. But with the orbital fleet yards gone and all Vox traffic scrambled, there was no way for the remaining Loyalist units on Calth's surface to communicate with one another or with Ultramarines command.Eventually, Magos Tawren and her Loyalist Skitarii forces managed to consolidate with the surviving Ultramarines of the 4th Company, including their commander, Captain Remus Ventanus. Assessing their desperate situation, Ventanus realised he had a vast horde of Chaos Cultists arrayed against his forces as well as hundreds of thousands of Traitor Astartes.The Traitors also possessed multiple battle groups of massive Traitor Titan war engines within their ranks. Magos Tawren suggested seeking refuge at Leptius Numinus, the old Imperial gubernatorial palace on the plains of Calth. Leptius Numinus possessed a non-active but functional data-engine as well as a high-cast Vox transceiver array.Though not currently operational, this equipment had been scrupulously maintained, and because the systems at the palace had been off-line when the Word Bearers began their assault, they might have been spared the scrapcode infection and electromagnetic pulse damage that had brought down networked communications all over the world. If the 4th Company and its allies could reactivate the data-engine at Leptius Numinus, they might be able to contact what remained of the XIIIth Legion's fleet in the Veridian System.This plan proved successful and the Loyalists reached the old palace. The commander of Tawren’s Skitarii suggested that they utilise their dedicated emergency manifold to power up the palace's data-engine and Vox assembly and contact other possible surviving Ultramarines, Imperial Army or Loyalist Mechanicus forces. Ventanus eventually established short-range communications with other besieged Ultramarines units. His situation was not unique. All of the Ultramarines on Calth's surface found themselves mired in the same predicament. None knew what had befallen their Primarch, Roboute Guilliman, or even whether he was still alive.Even as the 4th Company converged on Leptius Numinus, a large horde of Traitor forces commanded by the XVIIth Legion's Commander Morpal Cxir had already encircled the palace and launched an attack against its small group of valiant defenders. The Word Bearers used their vast hordes of Chaos Cultists as human fodder, driving them forward as they protected themselves from any significant counterattack.Terrible carnage was inflicted upon the Loyalist defenders by packs of horrific daemons summoned from the Empyrean as they punched through any breaks within the defensive line. As the assault grew more fierce, the defenders of Leptius Numinus prepared to sell their lives dearly, but they were spared from that dark fate by the timely arrival of the 4th Company and its heavy armour support.The reinforcements bolstered the defenders' resolve as they tore into the ranks of the Traitors and decimated their ranks. In the meantime, Tawren attempted to reactivate the data-engine and establish full communications with the remains of the Loyalists' fleet. Yet, Vetanus knew that although they were strong in spirit and well-armed, their forces could not hope to repel the Traitors' attacks indefinitely. It was only a matter of hours before the defenders' position would be overrun and everyone was slaughtered.Despite the brutality of the Word Bearers' assault, Tawren focused on her duties and managed to reactivate the dormant data-engine. With it, she was able to gather a clearer picture of the situation, especially the truly catastrophic scale of the losses: the enormous death toll, the systematic annihilation of the Ultramarines’ fleet, millions slain and entire cities aflame as burning debris plowed into the surface of Calth from orbit.Ventanus finally managed to contact Roboute Guilliman and provide him with a picture of what remained of the Loyalist ground forces on Calth. As many as 30,000 Ultramarines Battle-Brothers and 200,000 Imperial Army and Mechanicus warriors were still active in hundreds of scattered pockets of fierce resistance.Coordinated, they could achieve more than if they continued to fight alone and unsupported. In any other circumstances, Calth would have been declared lost to the Traitors, but the XIIIth Legion's fierce resolve prevented them from giving into despair. Roboute Guilliman believed that the situation could be salvaged and the Word Bearers made to pay a price that they had not expected.