Drop Site Massacre - Battle of the Urgall Depression: Though the Iron Hands, Raven Guard and Salamanders had managed to make a full combat drop and secure the Loyalist drop site, known as the Urgall Depression, they did so at a heavy cost. What had begun as a massed strike against the Traitors’ position was rapidly turning into one of the largest engagements of the entire Great Crusade. All told, hundreds of thousands Astartes warriors clashed on the dusky plains of Istvaan V. For all the wrong reasons, this battle was soon to go down in the annals of Imperial history as one of the most epic confrontations ever fought.Where one side lost ground in one place, it gained in another, and the battle lines shifted again and again, with no advantage pressed home on either side in the wake of such utter destruction wrought by both. The black sands ran red with blood. Tens of thousands of Space Marines had died in a little over two solar hours of battle; a cataclysm never before seen in open conflict, and tens of thousands more fought on, brutalised and injured. Such was the mind-shattering tumult, that scores of human auxiliaries, hardened even as they were by the wars of the Great Crusade, simply fell to their knees paralysed in terror, or became crazed and had to be shot down by their overseers, lest they endanger their comrades. Slowly, inexorably, the Traitor lines began to bow dangerously backward.As the slaughter at the fortress-line continued unabated, at the rearmost part of the Urgall Depression a vast crimson bulk had slowly descended, anti-aircraft fire stitching blackened scorches across its cylindrical armoured sides. It was a battle-maniple of the Legio Atarus, the Firebrands Titan Legion in their macro-lander, and their arrival had been warranted by the heart bloom-signatures of others of their kind advancing through the billowing dust storm from the desert plains. The Legio Mortis was approaching also, and at their colossal striding feet raced scores of Predator tanks and Outrider and Jetbike squadrons drawn from the Sons of Horus and World Eaters Legions.The auguries showed the Legio Atarus was outnumbered and outclassed. For the Legio Atarus, the chance to attack their erstwhile brethren of the Legio Mortis was not merely the desire of those who had stayed loyal to punish the Traitor, but the culmination of a long-simmering grudge that had its roots decades before this day. So it was that with righteous anger that the Titans of the Legio Atarus sounded their great sirens and charged into battle against their foe, and in doing so became the first Loyalist Titan Legion in the war of the Horus Heresy. The battle that followed was brief but brutal. At the cost of their own complete destruction, the Firebrands' counterattack effectively neutralised the secondary Legio Mortis contingent. The delayed and badly mauled Traitor Legion flanking force was then systematically destroyed by the Iron Hands subjugator group.The Urgall Depression was churned to ruination beneath the boots and tank treads of countless thousands of Astartes warriors and their Legion's armour divisions. The Loyalist Primarchs could be found where the fighting was thickest: Corax of the Raven Guard, borne aloft on black wings bound to a fire-breathing flight pack; Ferrus Manus of the Iron Hands at the heart of the battlefield, his silver hands crushing any Traitors that came within reach, while he pursued and dragged back those who sought to withdraw; and lastly, Vulkan of the Salamanders, armoured in overlapping Artificer plating, thunder clapping from his warhammer as it pounded into yielding armour, shattering it like porcelain.The traitorous Primarchs slew in mirror image to their brothers: Angron of the World Eaters hewing with wild abandon as he raked his Chainaxes left and right, barely cognizant of who fell before him; Fulgrim of the lamentably-named Emperor’s Children, laughing as he deflected the clumsy sweeps of Iron Hands warriors, never stopping in his graceful movements for even a moment; Mortarion of the Death Guard, in disgusting echo of ancient Terran myth, harvesting life with each reaving sweep of his great Warscythe.And then there was Horus, the former Warmaster of the Imperium, the brightest star and greatest of the Emperor's sons. He stood watching the destruction while his Legions took to the field, their liege lord content in his fortress rising from the far edge of the ravine. He was shielded and unseen by his brothers still waging war in the Emperor's name. At last, above this maelstrom of grinding ceramite, booming tank cannons and chattering Bolters -- the gunships, Drop Pods and assault landers of the second Loyalist wave burned through the atmosphere on screaming thrusters.The sky fell dark as the weak sun was eclipsed by ten thousand avian shadows, and the cheering roar sent up by the Loyalists at the arrival of their comrades was loud enough to shake the air itself. Like fiery comets from the heavens, the thrusters of countless drop-ships, landers and assault craft broke through the fire-shot clouds of smoke and descended to the Loyalist landing zone on the northern edge of the Urgall Depression. Hundreds of Stormbirds and Thunderhawks roared towards the surface, their armoured hulls gleaming as the power of another four Legiones Astartes came to Istvaan, their heroic names legendary, their mighty deeds known the length and breadth of the galaxy: the Alpha Legion, Word Bearers, Night Lords, and Iron Warriors.The Traitors, the bloodied and battered Legions loyal to Horus, fell into a fighting withdrawal without hesitation. Overwhelmed with rage, the headstrong Ferrus Manus disregarded the counsel of his brothers Corax and Vulkan and hurled himself against the fleeing rebels, seeking to bring Fulgrim to personal combat. His Veteran troops -- comprising the majority of the X Legion's Terminators and Dreadnoughts -- followed.