Sigismund - Return to the Throneworld: Many solar weeks passed after Dorn had heard and seen evidence of his brother's treachery. Sigismund remembered the rage in his gene-father's eyes. Dorn had wanted to go and confront Horus himself, to hear the traitor's confession and bring retribution with his own hands. But duty had held him back: duty to the Emperor and the Imperium that Horus now sought to destroy. They had returned to Terra, but Dorn had sent his sons as emissaries of his anger. He had named it a "retribution fleet."Thirty thousand Imperial Fists and over five hundred warships had struck out towards the Isstvan System, a force great enough to subdue a hundred worlds, bearing a brother's wrath. Now a second force from many Legions gathered to strike at Isstvan V, but no word had come from the retribution fleet.Though Dorn acceded to his first captain's request to stay by his side, Sigismund had kept the real reason to himself, sensing that the primarch would not understand. Sigismund barely understood it himself, but he had made his decision. That deception had weighed on Sigismund like penitent chains ever since.While overseeing the construction of the fortifications and defences of the Imperial Palace, Sigismund was present when Dorn received the tragic news of the Drop Site Massacre: the Imperial counter-strike had been massacred on Isstvan V. Vulkan and Corax were missing. Ferrus Manus dead. The Night Lords, Iron Warriors, Alpha Legion and Word Bearers were now with Horus. A primarch dead. Two lost. Three Legions gone, and four gone from friend to enemy in the space of a handful of words. Just as the vision Euphrati Keeler had shown Sigismund, this was the true beginning of the end.If four more Legions could turn against the Emperor, then why not more still? They would eventually come to Terra, and here the Imperial Fists must stand, and stand alone. Dorn ordered Sigismund to purge any remnants of the betrayers within the Sol System. He was allowed to use whatever and whoever he needed -- take them or destroy them as he must. Following this grievous news, Dorn ordered that the rest of the Imperial Fists Legion be recalled back to Terra, even if they burned through a thousand astropaths in order to reach the Throneworld.Later on, before leaving for Mars, Sigismund felt that he must reveal to his gene-father his true reasons for returning to Terra and why he couldn't take command of the Retribution Fleet. He shared with Dorn the truths revealed to him by the Remembrancer Euphrati Keeler. Enraged by his son's revelations, the primarch rebuked Sigismund. They were made to serve, he explained to the first captain, every primarch and every son of a primarch existed to serve the Imperium. Their existence had no other meaning. Their choices were not their own, their fate was not theirs to choose.Sigismund's will was Dorn's, and through his primarch, the Emperor's. Dorn had trusted him, and Sigismund had squandered that trust on pride and superstition, not unlike those who now rebelled against the Emperor. Shamed, Sigismund offered his blade to his gene-father to take his life, but the primarch refused. He would retain Sigismund as first captain, but none would ever know of what he had done. Dorn would not allow Sigismund's fear and pride to sow doubt in their ranks. His shame would be his to bear alone.Dorn then disowned Sigismund as one of his sons, for no matter what his future held, Sigismund would never again be one of his own.Yet Keeler had revealed to Sigismund that he would be needed before the end. His father would need him. He must bear whatever would come. Sigismund was thankful that he was still alive, and thus, he could still serve. He vowed that he would not fail.