Event · M31

Burning of Prospero

The Burning of Prospero, also known as the Battle of Prospero, was the Imperial invasion of Prospero, home world of the Thousand Sons Legion, undertaken early in the Horus Heresy. The dating of the event is not settled. A list of Thousand Sons battles gives the year 004.M31. Another account gives 734.004–005.M31. A separate table of Heresy battles places what it calls the First Battle of Prospero within the 005–006.M31 band, alongside the massacre on Isstvan III, and records a Second Battle of Prospero in 007–008.M31 as a later and distinct action, not the burning described here. These three datings are not reconciled. The events leading to the invasion began after the Council of Nikaea forbade the practice of psychic arts and the office of Librarian within the Legiones Astartes. Magnus the Red, defying this prohibition, projected himself to Terra to warn the Emperor that Horus had turned to rebellion. The projection breached the Imperial Webway and caused damage to the Emperor’s project there. Accounts of the Emperor’s reaction differ: one holds that the Emperor turned from Magnus in sadness, another that the Emperor was enraged and banished him from sight. Regardless, the Emperor ordered Leman Russ to bring Magnus to Terra in chains. Horus told Russ that returning Magnus alive would waste the effort expended, and sent five thousand Sons of Horus together with twelve Titans of the Legio Mortis to accompany the Space Wolves. Russ attempted to reach Magnus through Kasper Ansbach Hawser, though Hawser proved not to be the conduit sought. Russ then launched his attack on Prospero without any vox warning. Magnus concealed the approach of the Imperial fleet from his Legion and ordered the Thousand Sons not to fight. Orbital bombardment devastated the planet. A telekinetic shield maintained by the Raptora cult kept the city of Tizca standing against the bombardment. Ahzek Ahriman, Chief Librarian and First Captain of the Thousand Sons, refused Magnus’s order to stand down, and the senior captains of the Legion accepted his command in place of it; on the order of battle, Magnus is recorded as commander de jure while Ahriman stands as commander de facto. Ahriman led the Scarab Occult on the eastern approach to the city, later held the eastern sector of the defence, and ordered the defenders back when that line failed. During the fighting he engaged the Rune Priest Othere Wyrdmake on the aetheric plane, where he imparted to Wyrdmake the causes of the battle before giving Wyrdmake’s soul to warp predators rather than releasing him. Magnus himself joined the battle only late in its course, fighting Russ directly, and in its final act used Ahriman as the conduit for a spell that removed Magnus and the surviving Thousand Sons from Prospero to the Planet of the Sorcerers. One novel account numbers those carried away by this spell at one thousand two hundred and forty-two. Among the Imperial commanders present were Leman Russ, Captain-General Constantin Valdor, and Commander Jenetia Krole, with Bjorn counted among the Space Wolves engaged in the assault. The scale of the Thousand Sons and the losses inflicted upon them are recorded differently across sources, and these figures are not reconciled here. The novel A Thousand Sons presents the Legion as roughly ten thousand strong at the time of the invasion, with only about a thousand still fighting by the battle’s end and losses described as near ninety per cent. Inferno, by contrast, lists sixty-two thousand two hundred and ninety-two Thousand Sons defenders, and describes the Legion’s casualties in that account as near-total. A separate casualty account gives Imperial dead across the invasion at forty-nine thousand in total, comprising twenty-five thousand Space Wolves, twenty-three thousand Imperial Army personnel, almost five hundred Sisters of Silence, and scores of Adeptus Custodes, and gives thirty million dead among the civilian population and the Prospero Spireguard. Prospero itself was left a ruined world by the invasion. Those survivors of the Thousand Sons removed by Magnus’s final spell arrived at the Planet of the Sorcerers, and survivors of the Legion are recorded as having fought later at the Siege of Terra.

See where Burning of Prospero occurred on the galactic map during the Horus Heresy.

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