Time of Ending
The Time of Ending is one of the major time periods of the Imperium of Man. It was preceded by the Waning, stretching from mid-M41 to the end of M41. It is the "present day" of the 40k continuity.
The Time of Ending has seen the Tau emerge as a new power on the Eastern Fringe, Tyranids nomnomnom countless planets, and the Necrons begin to awaken from their sixty-million-year slumber. Failbaddon is starting his 13th Black Crusade, an event that would surely be exciting had it not been covered in depth a decade ago. Lugft Huron rebelled in the Badab War and is becoming a major Chaos warlord himself. Rebellions are running like wildfire and the astropathic choir on Terra is constantly bombarded by pleas for help. The Adeptus Mechanicus has found an issue in the Golden Throne that they can't fix.
All in all, a bad time to be a High Lord of Terra.
Damocles Crusade
Also called the Damocles Gulf Crusade, the Imperium tries to invade the nascent Tau Empire. At first, the campaign goes well, but the Tau soon slow the crusade to a standstill. Given time, the Imperium would decimate the Tau, but the First Tyrannic War begins, forcing the Imperium to call off the invasion. The Tau take note of their mistakes and start gearing their army towards facing the Imperium at large. The Imperium being Imperium learns nothing.
First Tyrannic War
The Imperium's first encounter with the Tyranids, which saw the Ultramarines First Company get nommed to a Marine and an entire world of Ultramar stripped of all life. We know most of you would be cheering the Tyranids on, but trust me, it's a bad thing.
The Siege of Vraks
As detailed in Imperial Armour Volumes Five, Six, and Seven, the munitions-stockpiling world of Vraks goes renegade under the guidance of the corrupt Cardinal Xaphan. The Death Korps of Krieg are called in to stem the rebellion. Seventeen years later, the siege finally ends with a full-scale Daemonic invasion and the intervention of the Grey Knights. Imperial forces "won", having spent countless resources and millions of lives to retake a now-worthless planet, polluted radioactively, chemically, biologically, and Nurgle-y (?), with all the ammunition stockpiled on Vraks (the only thing worth fighting for) spent during the siege.
The Saint Cyllia Massacre
A whole Titan Legion suddenly switches to Chaos, blowing up the planet they were stationed on and disappearing into the Warp. Yes, this is just as hilariously Awesome as it sounds.
Massacre of Sanctuary 101
An Adepta Sororitas outpost is built upon a Tomb World, with the Sisters inadvertently waking up its sleeping inhabitants and giving the Ordo Xenos its first concrete confirmation of the existence of the Necrons.
The Badab War
As detailed in Imperial Armour Volumes Nine and Ten, Lugft Huron, Chapter Master of the Astral Claws, becomes too big for his britches and slowly builds an empire on the outskirts of the Maelstrom. He's eventually brought to battle after firing on Imperial vessels, leading to a massive, Space Marine-focused war. He's eventually defeated, flees into the Maelstrom, and starts heading the Red Corsairs.
Second War for Amageddon
Ghazhgkull Mag Uruk Thraka gathers one of the largest WAAAGHs ever, laying siege to the vital hive world of Armageddon. Much badassery occurs, especially on the part of Commissar Yarrick.