The galaxy contains some four hundred thousand million stars. Only a fraction are presumed to have habitable planetary systems, and only a fraction of these have been investigated. Most are situated within the spiral arms between ten and forty thousand light years from the galactic centre. Even the human controlled Imperium, by far the largest and most widely distributed of all stellar empires, contains only a tiny fraction of the galaxy's stars.
Humanity is one of many races in the galaxy, but none are so widely distributed or so numerous as humans. Most occupy only a single world or a small group of worlds. Only a few alien races posses technology which rivals that of the Imperium - Orks, Eldar and Tyranids.
This is a time of superstition, in which unfathomable technology has been enslaved to the forces of mysticism and madness. To ordinary humans, scientific thought represents an abhorrent perversity, a corruption of honour and religious virtue. Even to those who deal with technology, science and magic have become inseparable. Warp engines must have runes engraved upon their sides, and lasers requires the blessing of the Gods of Battle.
This is a universe in which the gods, mysticism and magic are real.
9,000 BC: Building of the Sphinx, Great Pyramids.
750-314AD: Roman Empire.
2,011 (011/M02): Beginning of Second Epoch.
100/M02: Mars Terraformed.
200/M02: Mars is settled.
M03: Warp discovered.
M21: Navigator gene isolated, warp travel becomes even faster, Navigator families and cartels become powerful political entities. The Expansion of Humanity covers most of the galaxy, STC system is perfected to aid new colonies.
M26: Psychic humans begin to appear, simultaneously civilisation starts to collapse as widespread insanity and insurrection tear many colonies apart. Terrible wars sunder human space, demonic creatures possess unprotected psykers and subjugate worlds. This period is know as the Age of Strife. Warp storms isolate many parts of the galaxy including Earth.
M28: Earth devolves into petty fiefdoms ruled by warlords.
M28: Grunhag the Flayer, Ork Warlord, attacks the Squat Homeworlds with a huge fleet. This marks the beginning of Squat hostility towards Orks and distrust towards Eldar who stayed neutral in the conflict.
M30: Astronomican founded to make space travel easier.
M30: Age of the Imperium begins with the Great Crusade, for the next two hundred years, the Emperor and the Space Marine Legions gradually carve out the scattered Imperium of Man. During this time the Emperor is reunited with the Primarchs of whom the greatest is Horus.
007/M31: Horus Heresy begins. After several months, the Emperor orders seven Legions of Marines to assault Istvaan V; four defect to Horus, the other three are destroyed. Space Wolves attack Thousand Sons homeworld of Prospero forcing the Thousand Sons to declare for Horus and flee to the Eye of terror, during the pursuit the Thirteenth Company of the Space Wolves is destroyed in the warp.
014/M31: The Emperor, Rogal Dorn and Sanguinius teleport aboard Horus' war barge, Sanguinius is killed by Horus, Horus is killed by the Emperor. End of the Horus Heresy, Emperor incarcerated within the Golden Throne.
400/M32: Last of the Space Marine Primarchs dies.
500/M35: Greigor XI elected Ecclesiarch.
288/M36: Decree Passive issued by High Lords of Terra forbidding the Ecclesiarchy from maintaining an “armed force of men.” The Frateris Templar are duly disbanded but the Daughters of the Emperor remain.
437/M39: Volistad is re-discovered discovered by the Imperium in a state of planetary civil war between the four main families (Ochinka, Petchenka, Silenko, and Volga). House Petcherka is elevated to the position of Imperial Family.
981/M41: Navigator Durlan Ocellati discovers a route into the Wheel of Fire, a sector of the Ultima Segmentum that had previously been inaccessible.
986/M41: An Imperial patrol notes unexplained scenes of devastation in the Ork sector of Jakor-Tal. Adeptus Prefectus Primus Wilhelm Franz sends report on the Planetary Background of Volistad following Waaagh! Skroll.
997/M41: Imperial world of Piscina IV is attacked by Orks under the joint leadership of Ghazghkull Thraka and Nazdreg, Master Belial of the Dark Angels beats them off after a short but bloody campaign.