Isstvan III Atrocity - Lord of Wrath: In the wake of the failure of the virus bomb attack to annihilate the Loyalists, matters further spiralled out of hand. Even as Horus attempted to reestablish strategic control of the situation and order a second, conventional orbital bombardment, against orders and perhaps goaded by the response of those in his service, or as it has been suggested since, driven to grant the honour of dying by his own hand to those who had once served him, the Primarch Angron took matters into his own hands. Spearheaded by a wave of gunships and followed by a second Drop Pod wave, the World Eaters descended from their mighty flagship Conqueror with Angron himself and his chosen warriors at the fore. The Warmaster and his allies could only look on with outrage as the Primarch of the World Eaters made planetfall with a full 50 companies of his bloodthirsty Space Marines at his back, landing in the plaza areas to the west of the Precentor's Palace, hunting for their own kin with fratricide in their hearts. Their Thunderhawk and Storm Eagle gunships, strafing the now ash-strewn ruins, were met immediately with a sporadic return of fire, for they had found their intended prey.The "Red Angel" roared from the belly of his gunship onto the blackened bones that littered the plazas like fallen leaves in a winter forest, his great Chainaxes Gorefather and Gorechild screaming in anticipation of the slaughter to come. His challenge was quickly met as storms of weapons fire licked out from the shattered cityscape to find him, but he strode through it heedless, like a monster of dark myth made flesh. Behind him his World Eaters formed up in a great arrowhead of pale ceramite and glittering metal, eager for the slaughter to come. The forbidden rage-inducing cybernetic implants, known as the "Butcher's Nails," that were dug into their brains screamed the need to kill with cruel and irresistible force. Inevitably, from the line of shattered ruins that edged the plazas, their Loyalist brothers came, no less World Eaters, no less consumed by rage, a rage now fuelled to greater heights than they had ever known by the bile of tasted treason. Brother-Captain Ehrlen led them, a warrior whose tally of victories had been long in the service of the bloody creature he now faced. With him were a force of Loyalist Space Marines some 2,000 strong, a core of World Eaters who had sheltered with their commander in nearby garrison bunkers to wait out the storm of what they had been told (for believability's sake) was an Isstvanian suicide bio-weapon about to be unleashed, the rest of their Legion contingent scattered far and wide across the cityscape. For Ehrlen and his men the truth had been almost too terrible to face, and here and now, confronted by two-and-a-half times their number of those they had once called brother and the Primarch to whom they had pledged their lives, all set against them, it was simply too much. A homicidal madness overtook them and they determined to drag down as many of their former Battle-Brothers into death as they could claw and cut the life from.Both sides charged headlong at each other. Without tactics and without reason they charged into the arms of death, crashing against each other like competing waves of force. In moments, hundreds were slain as superhuman matched spite and fury against superhuman. Ehrlen was overwhelmed by dozens of World Eaters and dismembered, still spitting curses at those he had once called brothers, while charging Traitor Dreadnoughts exploded in the converging furnace heat of multiple Melta blasts, showering shrapnel and flame across the battle lines. In the carnage that ensued, a truth that was to become a bitter reality for years to come sprung fully formed into the reckoning of war; when Astartes fought Astartes, the usual Imperial logic of battle, of superiority of force, of an enemy's morale broken, of belligerents weighed and found wanting, no longer applied. Instead, matched in power and weapons, armour and skill, and above all in the unshakeable resolve to fight, the result was an appalling stalemate of expended force and savage attrition. Battle would now be characterised by superhuman bodies hacked and blasted until they could take no more, of weapons emptied in wrath and battle plate pulverised by not one blow but a score's counting before its wearer succumbed, but succumbed with the foe's blood on their hands as well. This would be a war in which no victor would escape the battle unscathed.In the slaughter of the Choral City plazas where 7,000 World Eaters smashed and butchered each other in a frenzy of violence, it would be the Traitors' numbers which finally turned the tide, that and the presence of their bloody lord. Angron was a machine made for killing, an unstoppable engine which sent torn bodies and shredded limbs tumbling away in looping arcs of crimson blood and spraying sparks of rent metal. He careened like a thunderbolt back and forth through the clashing press of armoured bodies, destroying everything that stood against him, shrugging off blade-strokes and Bolter shell strikes as if they were the mere bite of insects, roaring his challenges and calling out the names of the worthy dead his axes reaped. The killing continued until there were none left to kill and the ravaged victors, their once-white-and-blue armour now a gory red, stood amid a morass of shattered bodies, the filth of blood and clotted bone-ash around them like a spreading strain across the world.Upon viewing the horror that had been wrought, Angron is said to have exclaimed, "It is well done!" He then ordered his World Eaters to spread out through the city and seek more survivors to kill. So began the true bloodshed of the first inter-Legionary war, the first battle in the Imperium's history when its greatest defenders, the Space Marines, turned upon themselves in battle without quarter asked or given. Such was the shocking betrayal, the pain and price of treachery so great, that there could be no respite or relenting in such a battle, only bitter hatred and bloody vengeance.