Isstvan III Atrocity - War of Attrition: As night fell, the debris and dust thrown into the upper atmosphere by the planetary firestorm began to descend, the bleeding heat of the dying world birthing fresh continent-spanning rainstorms which ravaged the tortured air of Isstvan III and closed over the Choral City with renewed force. Hurricane-force winds drove great torrents of still-hot ash through the ruined canyons of city-blocks and tombstone structures peopled with the dead, while thunderous volleys of lightning played havoc with Vox-transmissions and Auspex surveys. Flight was virtually impossible and the surface all but cut off from the fleet. While the first stage of the plan, the separation of the Loyalists, had proved successful, the second phase was approaching unmitigated disaster, a fact that must have been readily apparent to the master-tactician that Horus undoubtedly was. Yet even masters of their craft, post-human and human alike, are subject to the whims of chance and action. The virus-bombing of Isstvan III had ultimately done nothing more than slaughter billions of innocent bystanders and turn Isstvan III into a hellish warzone of rubble, ash and storm which massively advantaged the defender while it vexed the attacker in turn.The overconfidence of the Emperor's Children had brought failure, and Angron's World Eaters had dispersed into the northern city in an uncontrollable and untrackable horde. Probing sweeps by Traitor aircraft had done little but suffer casualties, and revealed the scale of the Loyalist resistance and their bitter resolve to fight. The vicious fighting on Isstvan III saw the outnumbered Loyalists seeking to equal the strategic odds in their favour by dragging their enemies into conflicts in built-up areas and ruined landscapes where the full panoply of their Traitor foes could not be brought to bear upon them at once, resulting in running battles through corpse-strewn streets and shattered habitation blocks, blackened by fire and ash. Hundreds of hostile contacts had been flagged right across the sprawl of the shattered city, with particular concentrations identified in the northwestern zones, the Precentor's Palace area and the lethal tangle of the Siren Hold district. Horus and his commanders must have had no doubt that under the cover of darkness and the storm the Loyalists were on the move through and underneath the ruins of the Choral City, through catacombs, sewers and tunnel networks, consolidating, organising and fanning their lust for vengeance to a murderous heat.What was to come was to be a gruelling war of attrition where air power would count for little, and even though Horus had the Titans of the Legio Mortisat his command, he could not risk them in the city-ruins while the storm raged, blinding their scanners and defeating their advantage at range. Days became weeks as the tempest went on all but unabated, and beneath its cover, bitter close-quarter battles were waged between Loyalist and Traitor in the ruined city, the forces almost evenly matched in numbers. In the gaunt frameworks of habitation blocks and in the fetid darkness of sewer networks thick with corpse-waste, Space Marines battled Space Marines unto the death. The Traitors could only reinforce their assault piecemeal thanks to the storms, and during the worst of the climatic upheaval were forced into supplying munitions by Drop Pod if at all.In the wrecked industrial zones of the southern city, armoured columns of Vindicator and Predator tanks made grinding progress, battling block-by-block against brutal infantry counter-assault and suffering a toll exacted by Loyalist snipers and heavy weapons teams hidden in the twisted morass of factory ruins and toppled smoke-stacks.In the twisting shadows of the Siren Hold, warriors who had once proudly displayed the colours of the Warmaster and called themselves Sons of Horus defaced their armour and heraldry and reclaimed the name of the Luna Wolves once more. Their leader was Captain Garviel Loken, once a hero of his Legion and commander of its 10th Battle Company, and formerly part of Horus Lupercal's inner circle of Astartes advisers and friends, the Mournival. Singled out by the Traitors for his unwavering loyalty to the Great Crusade and its high ideals, Loken had been betrayed to his death on the surface like the rest, but now rose to the mantle of general and leader, coordinating resistance in the eastern and southern sectors of the city and masterminding a mobile defence of counter-thrusts and hit-and-run attacks that stopped his erstwhile comrades from employing the lethal encirclement tactics at which they excelled.Again and again Eidolon's Emperor's Children attempted to take the great granite bulk of the Precentor's Palace, only to be hurled back by Captain Tarvitz and his warriors, displaying implacable resolve and tactical excellence in their defence of the shell-shot edifice and its precincts. The palace was now further reinforced with recovered heavy weapons and patch-repaired vehicles claimed from the spoils of Eidolon's first failed attacks, and with the Loyalist Emperor's Children fought the mighty Ancient Rylanor, a Dreadnought of the III Legion, and to them he was like an undying icon of past glory and honour the Traitors had so hatefully cast aside. Many times was the Venerable Dreadnought thought lost, only to rise again from the rubble and fire his weapons to punish those who had betrayed the Emperor whose name they bore. The Traitors' attacks against the palace were further blunted by the need to guard their own flanks in the dust and darkness, as roving war bands of World Eaters, mostly Loyalist but some perhaps merely uncaring of their "allies" lives, attacked from the ruins and rubble, slaying and plundering arms and munitions before being cut down by disciplined fire or disappearing victorious back into the darkness.To the northwest, the Death Guard Loyalists faced the direst situation of the battle. Although heavily dug into the Isstvanian III bunker networks, trench lines and the screening city walls, and well-supplied with arms and munitions taken from the underground vaults of the planetary defence armouries, they were caught between the wrath of two implacable foes. From the inner city came Angron and his World Eaters, hammering again and again against their defences, hacking their way into tunnel networks heedless of casualties taken in the breach and leaving everyone within a red ruin of flesh and shattered ceramite. Beyond the city wall Mortarion, as implacable and relentless as Death itself, had braved the storm and landed the great relic-assault ship Omen amid the howling gales. Showing far more respect for the foe he faced than the Traitor Emperor's Children had, Mortarion had the Omen's turret guns sweep the ground clear, smashing the nearby trench networks and bunkers flat so they could provide no hiding place for a Loyalist ambush before unleashing its cargo. In defiance of the hurricane and the darkness, the Death Guard marched forth in ordered ranks, accompanied by the Legion's behemoths of war, including Spartan heavy assault transports and Fellblade and Typhon super-heavy tanks. The Traitors then began their systematic and relentless attack with the Reaper-Primarch marching slowly at their head, grimly counting the slain.