Vaxhallian Genocide

A horrifying example of the Chaos Space Marines of The Purge getting shit done by killing 14 BILLION people in the span of a month.

In 926.M41 the Purge decided to make the pretty Imperial world of Vaxhallia their next stop in their quest to kill everyone and everything ever. Showing up out of nowhere they proceeded to drop every kind of space daemon aids imaginable onto the bitch. Most of the planet was a graveyard by the time the Imperium responded. You see the planet was actually an Astropathic hub and fortress planet vital to the sector‘s defense, so when the Imperium got there it was primed to get shit of its own done, with the whole Hammers of Dorn, Fire Lords, and Crimson Fists chapters, a dozen guard battle-groups showing up, along with a few Knights from House Raven, just for good measure.

In response Typhus showed up with even more Plague Marines and a boat-load of zombies. Both sides stared each other down and an epic battle began as both strove to get the most shit done. In the end the Imperium lost as more and more of their own guard forces were turned into plague zombies. Oops. When the second Imperial force arrived the commander recognized the planet was screwed and began planning to evac the survivors and blow the planet to hell. This would of course kill anyone remaining on the planet and result in even more death, which was what the Purge wanted all along. Just as planned.

Timeline of Warhammer 40,000
The Times of Old Wars of Secession - War in Heaven (60.000.000 BC) - Fall of the Eldar (M30)
Pre-Heresy Age of Terra (M1-M15) - Dark Age of Technology (M15-M25) - Age of Strife (M25-M30)
Great Crusade (M31) The Last Church - Rangdan Xenocides - Interex - Faash - Council of Nikaea
Horus Heresy (M31) Battle of Isstvan III - The Burning of Prospero - Drop Site Massacre - Thramas Crusade
The Battle of Phall - Battle of Calth - Signus Campaign - Imperium Secundus - Siege of Terra
Time of Rebirth (M31-M32) The Great Scouring (M31) - Start of The Long War (M31) - The Legion Wars (M31)
The Battle of Skalathrax (M31) - Creation of the Codex Astartes (M31) - Second Founding (021.M31)
The Forging (M32-M34) The War of The Beast (544.M32-546.M32) - The Beheading (546.M32)
Nova Terra Interregnum (M34-M36) 21st Founding (M36)
Age of Apostasy (M36-37) Plague of Unbelief (310.M36)
Age of Redemption (M37-M38) Abyssal Crusade (321.M37-121.M38)
The Waning (M40-M41) Gothic War (143-151.M41) - The Macharian Crusade (392-399.M41) - The Macharian Heresy (400-470.M41)
Wars for Armageddon (444.M41, 941.M41 and 991.M41) - Damocles Crusade (742.M41)
Time of Ending (M41) The Vaxi Atrocity (731.M41) - First Tyrannic War (745-746.M41) - Sabbat Worlds Crusade (755.M41-780.M41)
Siege of Vraks (813.M41-830.M41) - Massacre at Sanctuary 101 (897.M41) - Badab War (901-912.M41)
The Vaxhallian Genocide (926.M41) - Second Tyrannic War (990.M41-993.M41) - Third Tyrannic War (997.M41-999.M41)
Octarius War (999.M41) - 13th Black Crusade (999.M41-M42)
Age of the Dark Imperium (M42-ongoing) Indomitus Crusade (999.M41-111.M42) - Ultima Founding (M42) - War of Beasts (001.M42-025.M42) - Plague Wars (~111.M42) - Psychic Awakening (M42)