Editing Shattered Imperium (section)

===The Isstvan War===
Magnus is summoned to Isstvan by his brother Mortarion. The Death Lord wishes to mend old wounds and hear more of Magnus' plans. Happy to hear that his brother has seen the light, Magnus sets out, with his two likeminded brothers, to bring the Death Guard into the fold.

When they arrive, the Ascenionist fleet finds not one, but three legions arrayed before them. The Death Guard, Iron Warriors and World Eater fleets wait patiently over Isstvan 3. Mortarion greets the Ascensionists and invites them to the capital city of Isstvan 3, to meet with their brother. Weary, but ambitious, Magnus accepts and leads his three legions to the surface.

He talks with Mortarion at length about the threat of Chaos and the the neccessity of knowledge. Perturabo seems the most receptive to Magnus's arguments and they discuss, at length the ascenionist plan. Suddenly, without warning, Mortarion's forces open fire on the Ascencionists. Magnus barely escapes the clutches of Perturabo. His own son, Ahriman, sacrifices himself for the Thousand Sons to escape the planet.

Battered and shocked, Magnus leads the Ascenionist fleet away from Isstvan 3 at best possible speed. As they reach Systems edge, an astropathic message is recieved. Prospero has been destroyed by the Space Wolves. Chemos and Medusa have been purged by the Night Lords.

Blinded by rage and grief, Ferrus Manus and Fulgrim turn their forces back toward their would be assassins. Magnus has no choice but to join his brothers or see them destroyed. What follows is a chaotic, violent maelstrom of void combat and planetary bombardment.

When word reaches the rest of the Imperium that 6 legions have turned on one another in the Isstvan system, the warmaster declares all of them traitors and rallies a force to cleanse them. The Sons of Horus, the Word Bearers, the Alpha Legion, The White Scars, The Raven Guard, The Salamanders and the Blood Angels. Seven legions to destroy six.

The Warmaster's fleet arrives to find both enemy fleets scattered, Isstvan 3 a lifeless husk and a brutal ground war underway on the barren world of isstvan 5. Horus orders Sanguinius to lead Corax and Vulkan to the ground on Isstvan 5 immediately. The Blood Angel gladly complies and deploys 3 assault legions to strike for the heart of the melee, where Magnus and Mortarion are locked in duel.

Nine legions, locked in a battle of cyclopean scale, await the second wave of loyalists. Instead, they are all of them betrayed. Horus begins an orbital bombardment of the battlefield, slaying Ascensionists, Loyalists and Free Legion forces alike. The Warmaster makes an announcement to the beleaguered forces below. They may join him in his new dark crusade to claim Terra, or they may die in the sand. All nine Primarchs spite the name of Horus. Amused but unsurprised, Horus prepares to destroy Isstvan 5.

On the ground, a truce is formed. The nine legions, battered and bloodied, forestall their current conflict in the name of survival. The ships of all nine legions focus their attention on the Warmasters fleet in the hopes of gaining enough time to evacuate the armies on the ground.

The fighting  is intense, and Horus is forced to surrender his position above Isstvan 5 to the overwhelming firepower of his foes.The Free Legions, Aided by the sudden appearance of the Nightlords, inflict heavy casualties on the Traitors before fleeing the system. 

Sanguinius and the Loyalists save the few remaining Ascensionists and flee towards Terra. Magnus repays the mercy of the Blood Angels by stealing several of their ships to carry his remaining followers towards some unknown goal on the edge of the Imperium.

Horus rallies his armies, declares a victory for Chaos and prepares to set his brothers to the task of carving up the Imperium.