Noctis Aeterna - Notable Events of the Noctis Aeterna: Battle of Lion's Gate - Roboute Guilliman defeats a massive daemonic assault by the forces of Khorne upon the Imperial Palace. After the Battle of Lion's Gate, informally known as the Second Battle of Terra, the High Lords of Terra realised that no place in the Imperium was now safe from an assault by the Archenemy.Defence of the Cadian Gate - The survivors of the fall of Cadia reinforce and successfully defend the remaining worlds of the Cadian System and the surrounding star systems of the Cadian Gate from the forces of Abaddon the Despoiler.Defence of the Damned - The Legion of the Damned appears to aid desperate Imperial defenders on more than a hundred worlds, including Baal and Armageddon.Chapter Worlds Lost - Contact is lost with slightly less than half of the 1,000 Space Marine Chapters known to be operating across the galaxy at the time the Great Rift was born in 999.M41. Twelve Space Marine Chapter homeworlds are known to be destroyed or overrun during this period, including Pranagar of the Sky Sentinels which was taken by the Daemon Primarch Magnus the Red and the Thousand Sons Traitor Legion, and Sabatine of the White Consuls.To Shield the Shrine Worlds - Shrine Worlds of the Imperial Cult come under assault by Heretic Astartes and Daemons across the Segmentum Solar and Segmentum Pacificus. The Word Bearers Traitor Legion is especially active in this endeavour. To combat the servants of the Ruinous Powers and end this blasphemy, the Black Templars Chapter takes it upon itself to launch Imperial Crusade after Crusade to retake each world. They are often joined by the Iron Hands, a score of other Adeptus Astartes Chapters, and whatever forces the Ecclesiarchy can muster.Indomitus Crusade - In the wake of the Battle of Lion's Gate, Roboute Guilliman gathers the largest armada seen since the time of the Great Crusade and leads his new Primaris Space Marine Chapters and an alliance of other Imperial forces on a massive counterassault across the galaxy against the Forces of Chaos and xenos threats. The Indomitus Crusade lasted for over a standard century and came to an end at the Battle of Raukos. After its end, Lord Commander Guilliman turned his eye to his Realm of Ultramar and its defence from his brother Mortarion and the servants of Nurgle during the Plague Wars.War of Beasts - The strategically located Hive World of Vigilus linked the Imperium Nihilus with the Imperium Sanctus through the Nachmund Gauntlet, one of the only known stable passes through the Great Rift. Realising the importance of this planet to the survival of the Imperium, it was assaulted by multiple xenos and Chaos forces, including the Black Legion under the command of Abaddon the Despoiler. Though the Despoiler's invasion was ultimately defeated by warriors drawn from multiple Space Marine Chapters under the command of the Ultramarines Chapter Master Marneus Calgar, Vigilus remained a world largely under siege from Ork, Drukhari and Genestealer Cult factions.War Zone Armageddon - As the forces of the Orks and the Imperium were still battling amongst the ruins of the Hive World of Armageddon, the world was overrun by the daemonic legions of Khorne and Tzeentch, which soon began to assault each other as well as anything else in their way. The Greenskins and the humans were often forced to forge alliances of convenience to defend themselves against their common foe. The arrival of reinforcing Imperial forces, accompanied by elements of nine Space Marine Chapters led by the Salamanders, ultimately succeeded in halting a ritual that would have brought Angron, the Daemon Primarch of the World Eaters, back to the planet that had defied him centuries before during the First War for Armageddon.Devastation of Baal - With the arrival of Roboute Guilliman's Indomitus Crusade, the Blood Angels and their Successor Chapters are successful in fending off the great assault of Hive Fleet Leviathan upon their homeworld of Baal. The remainder of the Leviathan is largely consumed by a Warp Storm and a great assault of Khorne Daemons led by the Blood Angels' ancient foe, the Bloodthirster Ka'bandha.Fourth Sphere Expansion - The T'au Empire's Fourth Sphere Expansion was aborted by the birth of the Great Rift when its forces were destroyed by the catastrophe sweeping the galaxy. However, once stability had returned to the Immaterium, the T'au would launch their Fifth Sphere Expansion campaign in the early 42nd Millennium.Absorption Wars - It has always been the wish of the Necron Overlord Imotekh to reunite all the Tomb Worlds of the Necron species beneath his rule and nothing could deter his plans, not even rampant daemonic incursions. As the Great Rift opened, the Stormlord launched his Absorption Wars, a many-pronged campaign to seize dozens of Tomb Worlds awakened by the Warp influx. Imotekh sought to conquer them before they could fully rise from their stasis slumber, ensuring the continued rise of his Sautekh Dynasty.Blood Crusade - The Blood Crusade was a massive offensive unleashed by the forces of Chaos loyal to the Blood God Khorne. His followers -- from Daemon legions to brutish beasts to violent-minded hive city Chaos Cultists -- all took up that call to arms. Riding new crests of the Warp Storms known as the "Blood Waves," the Daemon legions erupted from the Cicatrix Maledictum, bringing new orgies of slaughter across the galaxy. Thus began the Blood Crusade. The red-raged armies did not seek out destinations. Instead, the gore-slavering fiends merely rode where the storms took them, materialising upon a planet to unleash carnage, and leaving when the tempests moved beyond. Eight distinct spearheads drove out into the galaxy in all directions, and as blood-trails draw in predators, so too did the Blood Crusade.Red Tide - The Red Tide is an enormous Chaos horde that erupted out of the Warp in the wake of the Great Rift's birth. The Red Tide had no plan or agenda beyond destruction, and was simply a carnage-filled crusade of wanton slaughter that carved a bloody path across the galaxy.Invasion of the Stygius Sector - In the wake of the birth of the Great Rift following the 13th Black Crusade of 999.M41, Tzeentch looked upon his brothers. Without plan or agenda, Khorne and Slaanesh were glutting themselves on slaughter and torment, consumed by their rampages, but when Tzeentch saw Nurgle corrupting a whole realm in Ultramar, he grew jealous, seeking as ever to conspire against him, but also wishing to seize star systems for his own. So did the Architect of Fate put a million plans in motion. The Crystal Stars intrigued Tzeentch, as did the Shrouded Zone. It was the Stygius Sector, however, that he would attempt to claim first. It was in the Segmentum Obscurus, near the Eye of Terror and cut off from the Light of the Emperor's Astronomican during the Noctis Aeterna. There, entropy raged the fiercest, and amidst the maelstrom of unnatural energies the tightly packed pattern of nine-times-nine star systems called out irresistibly to Tzeentch. Though the assault was contested by a powerful Imperial force and even aid from the Aeldari of Craftworld Ulthwe, the sector was ultimately surrendered to Tzeentch, who saw it as only the first of the regions of realspace he intended to claim for his own.Plague Wars - The Plague Wars were the result of Nurgle's desire to claim the Realm of Ultramar for his own. After the creation of the Great Rift, the forces of the Plague God, led by his foremost champion, the Daemon Primarch Mortarion of the Death Guard Traitor Legion, claimed the Scourge Stars, a trio of star systems from which Mortarion led his invasion of Ultramar. The wars raged for solar decades across Ultramar as the Imperial defenders slowly lost ground. The Chaos offensive was finally brought to a halt by the return of Roboute Guilliman following the end of his Indomitus Crusade in the early second century of the 42nd Millennium. The battle between the former brothers ultimately resulted in a draw on Iax, though the conflict remains ongoing.