Important Lore Events Introduced so far…
All this information was pulled from the website lexicanum and others
War in Heaven approximately 60 million years before the 41st Millennium
The War in Heaven, also known as the War of Aeons among the Necrons, was an ancient and devastating conflict fought between the humanoid Necrontyr xenos later known as the Necrons, their C'tan allies and the Old Ones. The war was fought over sixty million Terran years before the 41st Millennium.
With the power granted by the C'tan, the Necrons ultimately proved victorious over their hated Old One adversaries, relegating that ancient species to extinction or to flight from the galaxy.
But the suffering and destruction unleashed by the war cascaded through the Immaterium, ultimately destabilising it and unleashing the plague of Enslavers that almost destroyed all sentient life. At the same time, the ancient Aeldari -- a psychically powerful species created by the Old Ones during the war -- began their rise to galactic mastery.
After overthrowing the rule of their C'tan masters, the Necrons chose to retire to their Tomb Worlds and enter the Great Sleep, waiting until the plague had passed, their own divisions and discord had faded into irrelevance and the Aeldari civilisation had passed its peak.
Birth of Slaanesh Early M30
Slaanesh was born in the early 30th Millennium (roughly early M30), coinciding with the culmination of the Fall of the Aeldari. The Chaos God's birth was caused by the collective excess, hedonism, and psychic reflections of the Eldar empire, creating the Eye of Terror and ending the Age of Strife.
The Unification Wars 712.M30
The Unification Wars were a series of brutal, defining conflicts in Warhammer 40,000 lore, where the Emperor of Mankind forged the Imperium by conquering Terra's warring "techno-barbarian" states. Using genetically engineered Thunder Warriors, the Emperor dismantled petty tyrants, unified the planet, and prepared humanity for the Great Crusade.
Primarchs Scattering 792.M30
The Primarchs were scattered across the galaxy by the Chaos Gods (or their agents/collaborators) who breached the Emperor's secure laboratory beneath the Himalayan Mountains on Terra. This event, occurring during the early stages of the Great Crusade, tore the gestation capsules away and sent them to various worlds. The Perpetrator: While traditional lore points to a direct attack by the Chaos Gods, in the Siege of Terra series, it is revealed that Erda, the biological mother of the Primarchs, scattered them to protect them from the Emperor's destiny, though she may have been manipulated by Chaos.
Method: A massive warp rift was created in the laboratory, allowing the forces of Chaos to breach the protections (Gellar fields) surrounding the capsules.
The Purpose: The goal was to destroy or corrupt the Emperor's sons. The scattering forced them to mature in isolation on often brutal worlds, shaping their unique personalities and skills.
Impact: This act of sabotage is considered a pivotal moment that crippled the Emperor's initial, perfect plan for the Great Crusade.
The Great Crusade 798.M30
The Great Crusade was the period in the early history of the Imperium of Man, lasting from approximately 798.M30 into the first decades of the 31st Millennium (approximately a little over two standard centuries), when the Imperium was expanding as it sought to bring all of human-settled space back under the control of a single ruler, the Emperor of Mankind.
The Great Crusade marked a brief era in human history of rebuilding, reunification and rapid technological advancement following the complete regression of Mankind into techno-barbarism during the 5,000 Terran years of the Age of Strife. It was a time when the Emperor of Mankind still lived in the conventional sense and led His people in person. The Great Crusade era is considered the Golden Age of the Imperium before the long, slow slide into cultural stagnation, political repression and increasing warfare that marked the ten millennia after the Great Crusade and the Horus Heresy had ended.