Lord Commander of the Imperium - History: The position was first created for Primarch Rogal Dorn, the Praetorian of Terra, who held it during the Horus Heresy so that he might coordinate the defence of Terra from the attack by the Traitor Legions of the Warmaster Horus. After the Heresy, the office was officially added to the ranks of the Senatorum Imperialis -- the twelve most powerful individuals in the Imperium's governmental hierarchy.Though history does not record the names of those first High Lords of Terra, the tradition of the Ultramarines Chapter relates that their primarch Roboute Guilliman was one of them. He became the first lord commander of the Imperium and Imperial Regent after the Heresy, receiving the rank from Rogal Dorn so that he could stabilise the Imperium and begin the reforms of the Time of Rebirth. He was the only man ever to command the entirety of the Imperium's armed forces after the Heresy. Before the Heresy, this function had been administered by the Terran War Council and the Imperial Warmaster.Guilliman's directives single-handedly reshaped the Imperium, restructuring its administrative and military apparatus following the internment of the Emperor of Mankind within the Golden Throne on Terra. Guilliman would continue to hold this title, acting as both chair of the Senatorum Imperialis and the Imperium's military commander-in-chief, until he was fatally wounded by the Chaos-tainted blade of the Daemon Primarch Fulgrim of the Emperor's Children Traitor Legion at the Battle of Thessala in 121.M31.The dying Guilliman was subsequently put into temporal stasis on the verge of death and his body placed upon the throne that lies in the Temple of Correction on the Ultramarines' homeworld of Macragge. The title of lord commander of the Imperium continued to be used for a time following Guilliman's internment, and the later lord commanders served as both the chairs and first among equals on the Senatorum Imperialis and as the supreme commander of the Imperium's military.In honour of the primarch, the later lord commanders of the Imperium were often simply referred to as "Lord Guilliman." This honorific was no longer in use by the 41st Millennium, but is known to have been in continuous use at least until the mid-32nd Millennium. At that time, the individuals known to have served as lord commander of the Imperium included the High Lord Udin Macht Udo and the Adeptus Astartes Chapter Masters Koorland and Maximus Thane.In the aftermath of the War of the Beast and the disastrous event known as The Beheading in 626.M32, the position of lord commander of the Imperium was abolished until ca. 999.M41, when the resurrected Roboute Guilliman returned from his millennia-long dreamless slumber on Macragge to Terra during the Terran Crusade.Following his meeting with his father the Emperor in the Imperial Palace for the first time in ten thousand standard years, Guilliman informed the sitting High Lords of Terra that he was once more taking up the mantles of the lord commander of the Imperium and Imperial Regent.Upon his resumption of the rank, Guilliman forcibly removed five High Lords from office and hundreds of lesser lords and replaced them with individuals of his own choosing. The resurrected primarch also warned the High Lords of an encroaching darkness, a terrible Warp phenomenon called the Great Rift that was even now manifesting itself across the galaxy from end to end. For all the disturbing omens and disastrous losses, Guilliman urged Humanity's leaders not to give up hope. The Emperor of the Imperium was not blind to their plight, and neither was its restored lord commander.Under Guilliman's direction, vast armies and armadas were raised in numbers not seen since the Great Crusade that had founded the Imperium ten millennia before. A dark new age called from amidst the fires of endless war, and the Imperium of Man would answer -- with the Indomitus Crusade.