Editing Age of the Dark Imperium (section)

==Noctis Aeterna==
''Main article: [[Great Rift]]''

Also known as the Blackness in Low Gothic, the Noctis Aeterna was an event caused by the formation of the Great Rift where the light of the Astronomican vanished and Daemonic incursions ran rampant. The event appeared to distort time itself, lasting a few days on some planets, while on [[Terra]] it lasted for just over a month (and it's speculated that it's still going on for some unfortunate planets). Judging by the time-frame presented in Watchers of the Throne: the Emperor's Legion, the Noctis Aeterna began a few months after the Fall of Cadia and partway through Roboute Guilliman's voyage to return to Terra, although the aforementioned time distortion means it is only an accurate timeline from Terra's perspective. From Baal's perspective, it only lasted a day or two, yet when it cleared up the Blood Angels had discovered that seventy years had passed in the outside galaxy. The event culminated in an army of Daemons of Khorne invading Terra itself. While this was repulsed thanks to Guilliman and the Custodes, the attack still shook the Imperium to its core as it proved that the influence of Chaos was stronger than ever before and that even the Throneworld was no longer safe from its reach.

The consequences of this left major wounds that have still yet to heal. The Imperium lost contact with half of all known Space Marine Chapters, and twelve chapter homeworlds were confirmed to be destroyed. Every Eldar Craftworld was assaulted by Chaos forces (including the ones hidden in the Webway), and they have yet to account for the fate of two of them. Armageddon was transformed into a half-Daemon World, turning the war between Orks and humans into a four-way clusterfuck as Daemons of Khorne and Tzeentch joined in on the fun. On the positive side, the Blackness unintentionally managed to save the Blood Angels, as it allowed Ka'Bandha to destroy the tendril of Hive Fleet Leviathan attacking Baal as the Great Rift dragged many of the Hive Fleet's bioships into the Warp.

From this point forward, attempts at forming an objective chronology become increasingly pointless due to the continuing time distortions across the galaxy; most worlds end up using the formation of the Great Rift as their new "Year Zero" as a result, conveniently timed at 000.M42 thus keeping the calendar somewhat intact for out of universe purposes. In-universe, Guilliman determines that that the year is possibly between 200 to 1000 years off either way.