Shadow of the Emperor - Ultimate Fate: In response to the treachery of the Warmaster Horus and his betrayal of the Loyalist Astartes in the Sons of Horus, Emperor's Children, World Eaters and Death Guard Legions at Istvaan III, the Primarch of the Imperial Fists Legion, Rogal Dorn, on the direction of the Emperor who had learned of Horus' actions from the Loyalist survivors aboard the Eisenstein, ordered 7 Loyalist Space Marine Legions to Horus' base on the world of Istvaan V to challenge the Traitors. They would attack in two waves and fall under the supreme command of the Iron Hands' Primarch Ferrus Manus.The Legions comprising the first wave were the Iron Hands, Salamanders, and Raven Guard. The Legions comprising the second wave were the Alpha Legion, Night Lords, Iron Warriors, and a large contingent of Word Bearers that their Primarch Lorgar had stationed in the star system. Unknown to Dorn and Ferrus Manus, the Night Lords, Alpha Legion, Iron Warriors and Word Bearers had all turned from their service to the Emperor and pledged their loyalty to Horus, and been instructed to keep their new allegiance to Chaos a secret.The Iron Hands, Salamanders and Raven Guard were deployed in the first wave of the assault on the planet while the Shadow of the Emperor and the rest of the flotilla of Loyalist vessels provided overwatch of the planetary assault, standing by in case they needed to provide assistance to the attacking ground forces. After they secured the drop site, they were to have been followed by the arrival of the other four Legions.The first wave won the drop site at a heavy cost. Horus ordered his front line troops to fall back, tempting Ferrus Manus to overstretch his already thin lines. Against the advice of Corax and Vulkan, Manus led his Veterans against the fleeing Traitor Marines unsupported. Manus then brought his brother Fulgrim to combat.As the two Primarchs drew their weapons, the Raven Guard and Salamanders fell back to regroup and allow the second wave's Legions to advance and earn glory. However, as they returned they were mowed down by the four Traitor Legions that had landed to supposedly support them, thus revealing their new allegiance to Chaos. Horus then pressed his own attack and sandwiched the Loyalists between the two Traitor forces, killing most of them.When the Traitors opened fire on the first-wave of Loyalist Astartes, the Shadow of the Emperor received their stand-to and distress broadcasts. It was cut off within a matter of solar minutes, jammed by the Traitor warships in orbit. It was too soon for the Reflex Shields to be raised, and against such numbers that were arrayed against them, that would have been the only defence.The Terminus Est, under the command of First Captain Calas Typhon, was one of the few capital ships of the Death Guard Legion. When the Traitors revealed their treachery, the Terminus Est suddenly engaged and treacherously destroyed the unprepared Shadow of the Emperor. It is argued by many Imperial scholars that this engagement was the earliest recorded conflict between Battleships that were specialised to carry Attack Craft.The engagement was swift and brutal, depriving the embattled Loyalist forces on Istvaan V of any air support in the massacre that followed. The loss of the Shadow of the Emperor is remembered to this day as one of the greatest losses of the Raven Guard in the Horus Heresy and the Chapter maintains a long-standing grudge against the Death Guard as a result.