865.M30 Battle of Rennimar - This was a great Imperial Compliance campaign conducted by the Imperial Fists Legion against the massive Ork WAAAGH! of the Over-Tyrant of Grel in the Rennimar System, who was himself already under siege by both the Death Guard and Space Wolves Legions. Rogal Dorn, alongside Captain Archamus, the commander of his Huscarl honour guard, led a force of 10,000 Imperial Fists against the Greenskin forces. Typical of the VI Legion, they established heavy-walled bulwarks on the planet Rennimar, which enticed the Orks to hurl themselves futilely against the Imperial Fists' stalwart defences. This enabled the Legiones Astartes to utterly crush their xenos foes.
865.M30 Discovery of Jaghatai Khan - After conquering the Feral World of Chogoris with a great nomadic army of steppe horsemen, Primarch Jaghatai Khan encounters the Emperor arriving with the Great Crusade's Principia Imperialis Expeditionary Fleet. Faced with submission or subjugation, the Great Khan pledges his sword to the Imperium and claims command of the V Legion -- his White Scars.
866.M30 The Grael Library - The crowning achievement of the world of Riohbia, the self-proclaimed warlocks guarding the proscribed works of the Grael Library refuse to yield its contents to the Imperium. The XIX Legion, prosecuting the campaign of Imperial Compliance in the system, are tasked with quashing the psychic threat and destroying the library. En route, however, they receive a communique stating that a passing fleet of the Thousand Sons Legion has intervened and dealt with the threat already.
869.M30 Compliance of Molech - The newly discovered Knight World of Molech is brought into Imperial Compliance through a massive joint-Compliance campaign carried out by multiple Legiones Astartes. Cyprian Devine of House Devine is named Planetary Governor of Molech. In the presence of several of His Primarch sons, the Emperor leads them to a Warp Gate on the world, where He proceeds to enter the Realm of Chaos to parley with the Ruinous Powers. When He returns, the Emperor appears aged, but much more powerful. He then psychically suppresses his sons' memories of Molech and stations a large garrison force comprised of nearly 100 Imperialis Auxilia regiments, three Legio Titanicus cohorts, and detachments from two Space Marine Legions to protect the secrets of the Warp portal on Molech -- a gateway into the Realm of Chaos that the Emperor has used before, during humanity's golden era of the Age of Technology.
ca. 839.M30 - ca. 890.M30 Rangdan Xenocides - The Titans of the Legio Gryphonicus as well as the Legio Vulturum, the Legio Kydianos and other Xanithe Mechanicum forces from Xana II served alongside the vaunted Dark Angels Legion during the vital campaign known as the Rangdan Xenocides. The Dark Angels hurled themselves at the enemies and broke their greater strength in countless battles against the xenos on the edge of the Halo Stars. This campaign culminated in the Third Rangdan Xenocide around 890.M30, which resulted in the loss of the lives of 50,000 Space Marines spent in preventing the destruction of perhaps the entire northern Imperium by the alien menace from the outer darkness. Due to the extensive losses suffered by the I Legion, by 899.M30, the Ultramarines Legion was on the cusp of becoming the largest of the Legiones Astartes, standing at around 166,000 Legionaries.
876.M30 Compliance of Zavarich - The Feudal World of Zavarich, located within the Cyclops Cluster region, is brought bloodlessly into Imperial Compliance by the 611th Expeditionary Fleet. Shortly thereafter, Zavarich enters into operation as a fully managed Agri-World by the time of the Horus Heresy's outbreak, and is notable for being one of a relative handful of such worlds in the region.
881.M30 The Majind Tore Transgression - During the devastation of the Second Rangdan Xenocide, a Basemekanic Barq breaks the cordon of the galactic northeast to make impact at Majind. The Death Guard Legion in pursuit are decimated as the Macrobeest within is activated by unknown means. Only the quick thinking intervention of the VI Legion prevents disaster.
891.M30 Crisis of the Hungering Gyre - The Mechanicum forces of Gryphonne IV, along with their resident Legio Titanicus forces from the Legio Gryphonicus, fought an unknown xenos menace known as the Hungering Gyre, and arose victorious amid great personal sacrifice. In recognition of their great service during this campaign, the Emperor decreed that Paramar V and its industrial facilities would be granted as a vassal domain to the distant Forge World.
Late 800s.M30 Discovery of Lascal - The terrestrial world of Lascal was discovered on the edge of the Grail Abyss by the 7th Expeditionary Fleet under Lord Commander Suleiman Grimm of the I Legion. Originally it had been a Feral Ork holding before the Dark Angels exterminated the Ork infestation. Lascal became a forward outpost of the Great Crusade, and later a naval fleet anchorage was constructed there in orbit under the auspices of the Lucien Mechanicum. Continuing to grow, by 902.M30, Lascal had become an independent and self-sustaining Imperial colony.
891.M30 Discovery of Grail - The Expeditionary Fleet of Rogue Trader Corthona Van der Veld discovered an errant Dead World and named it Grail. This world's namesake is later given to the region known as the Grail Abyss, a place of hidden wealth and terrible danger which has long drawn Explorators and would-be Imperial treasure-hunters to their graves.
896.M30 Discovery of Konrad Curze - Stranded on the sunless world of Nostramo and plagued by precognitive visions, Primarch Konrad Curze becomes known as the "Night Haunter" for his brutal enforcement of justice. When the Emperor finally arrives, alongside several of His primarch sons, including Magnus the Red, Rogal Dorn and Fulgrim, as well as representatives from the Ultramarines Legion, Curze experiences a vision so terrible he tries to claw his eyes out -- nevertheless, he is placed in command of the VIII Legion -- which he reshapes into the fearsome Night Lords, who specialise in the use of terror as a weapon.
899.M30 Xenocide of the Osiran Psybrids - A sub-fleet of the XII Legion, under the command of Praetor Erad Krüg, was fighting on the southwestern extreme of the Great Crusade's frontier near the Eurydice Terminal, against Ork raiders of the self-styled Glortian Empire from the untracked abysses beyond. As both sides fought one another, they were suddenly set upon by a mysterious third party -- the deadly xenoforms known as the Osiran Psybrids. As nightmarishly powerful xenos teleported aboard the War Hounds' vessels, only their savage tenacity allowed them to survive, as they lost dozens of their own voidships and hundreds of Ork vessels were shattered. Primarch Roboute Guilliman ordered the War Hounds to hold at all cost, and if possible, to track the Psybrids' vessels to their source. The Ultramarines despatched a powerful Retribution Fleet to the Eurydice Terminal, and soon joined their fellow Legion. With their combined might, the Ultramarines systematically wiped out the Psybrids, and when they died, so too did their slave armies. The Astartes soon made short work of the remaining Glortian Orks as well, driving them into the outer darkness. The blood price of the battle had been high, but it was a price the Ultramarines were willing to pay to avenge the defeat they had suffered nearly six solar decades earlier during the Osiris Rebellion.
899.M30 Discovery of Angron - The Emperor arrived at the world of Nuceria, where he observed his long-lost son, the Primarch Angron Thal'kyr, lead a revolt of slave-gladiators against their cruel overlords. Angron had been found after his arrival on Nuceria as a young adolescent and sold into slavery. He then underwent horrific surgery, where barbaric cybernetic cranial implants known as the Butcher's Nails were inserted into his brain to increase his aggression. Thrown into the fighting pits for his masters' pleasure, he soon rose to the top, and became the "Lord of the Red Sands." On the eve of the largest gladiator exhibition ever held by the slave masters of the city of De'shea, Angron led a successful slave revolt and escape by many of his fellow gladiators. Taking refuge within the De'shea Mountains, the night before their final confrontation with their cruel overlords, Angron dug his own grave, ready to die alongside his brothers and sisters in the name of freedom. But before the battle took place, the Emperor intervened and teleported Angron aboard His own flagship, unwilling to see one of his primarchs slain before he could be put to use in the Great Crusade. Angron's fellow gladiators were slain to the last man and woman. Angron is enraged that he was denied an honourable death alongside his beloved comrades, and swears never to forgive the Emperor. Angron was then examined on Terra and given over to his genetic sons from the XII Legion, the War Hounds. After assuming command, he reshaped his Legion in his own savage image, and they became the World Eaters.