The Rangdan Xenocides were a series of xenocidal campaigns carried out against the xenos threat known as the Rangdan Cerabvores during the 860s of the 30th Millennium during the latter years of the Great Crusade. These wars were the most terrible of any yet fought by the Expeditionary Fleets of the burgeoning Imperium of Man. The threat was only stymied after the intervention of the Emperor Himself and at least three Space Marine Legions, over a dozen Legio Titanicus Titan Legions, several Imperial Knight Houses, the military forces of the Mechanicum and hundreds of thousands of troops of the Imperialis Auxilia.
When the Imperial Expeditionary Fleets of the Emperor's Great Crusade at last had breached the Eastern Fringe of the galaxy, they inadvertently attracted the attention of the Rangdan Cerabvores, a species of such macabre power and technological might it seemed, for a time at least, that the Imperium had met its doom. Facing waves of attack from the galactic east and north, and suffering losses that would not be exceeded until the dark days of the Horus Heresy, the wars of the Rangdan Xenocides were the most terrible of any yet fought. Whole Expeditionary Fleets went to their deaths without a single survivor, worlds were laid waste, dozens of Titan Legions were obliterated and by the end, entire Space Marine Legions (exactly which Legions were affected was purposely redacted from Imperial records) had been lost to the Imperium. Much of what happened during this abyssal conflict is still locked under seal, but what can be said is that with the breaking of the Labyrinth of Night by the Emperor, the threat was at last stymied. What remained was for the Rangdan taint to be purged in a subsequent standard decade-long series of bio-pogroms that left entire human inhabited sectors lifeless to ensure what was hoped to be a final victory. It was then given to the Space Wolves of the VI and the Dark Angels of the I Legions -- the latter who had suffered themselves so very dreadfully against the horror -- to conduct these purges, as these two Legions were entrusted above all others to do what had to be done.
The Titans of the Legio Gryphonicus as well as the Legio Vulturum, the Legio Kydianos and other Xanite Mechanicum forces of Xana II served alongside the vaunted Dark Angels Legion during this vital campaign. The Dark Angels hurled themselves at their enemies and broke their greater strength in countless battles against the vile xenos on the edge of the Halo Stars. This campaign culminated in the Third Rangdan Xenocide around 890.M30, which resulted in the loss of the lives of 50,000 Space Marines spent in preventing the destruction of perhaps the entire northern Imperium by the alien menace from the outer darkness. Due to these extensive losses suffered by the I Legion, by 899.M30 the Ultramarines Legion was on the cusp of becoming the largest Space Marine Legion, with a strength of around 166,000 Astartes.
Horus Lupercal and his Luna Wolves Legion, who had been otherwise occupied in the ongoing wars in the galactic west, were now firmly in the ascendance in the eyes of the Great Crusade following the Xenocides. The future of the next few standard decades of Imperial conquest and expansion now rested with him and the other Astartes Legions that retained their strength.
- Juljak Nul, "The Storm Walker" - Nul had the dual distinctions of being the first Master of Ordnance of the XII Legion, later known as the War Hounds, and serving as one of the first of that Legion's officers interned within a Dreadnought frame after being horrifically mutilated by Slaugth murder-minds at Rangda. The fact that Nul was horrifically wounded by the Slaugth is perhaps a clue to the true nature of the mysterious "Rangdan Cerabvores" faced by the Imperium's military forces.
- Crysos Morturg - Crysos Morturg was an Astartes of the Death Guard Legion, who was neither of Terra nor Barbarus by birth, but instead taken in with an emergency influx of recruits from the induction pool of the 18th Expeditionary Fleet after the Death Guard suffered near-catastrophic losses in the Rangdan Xenocide campaign. Years after his induction, he would manifest latent psychic abilities and was banished to the Legion Destroyer Corps, whose units were tasked to the brunt of the worst fighting the Death Guard endured. He was marked for death on Istvaan III, but would not die, and went on to become one of the most deadly commanders of the Loyalist resistance. Morturg miraculously survived the slaughter of the Istvaan III Atrocity and later became a Blackshield in a quest for revenge upon his former brothers.
- The Nemean Reaver - This unknown Blackshield Reaver Lord fought throughout the middle years of the Horus Heresy, leading the Blackshield band known as the Dark Brotherhood against numerous foes as he sought to carve out a haven within the Eridayn Cataract. He garnered a reputation throughout the Pale Stars and was often referred to simply as the Nemean. It is generally believed that he was once an officer of the I Legion -- the Dark Angels -- though even this was far from certain. Unconfirmed rumours circulated that he was a survivor of the Rangdan Xenocides, the apocalyptic conflict that saw the nascent Imperium threatened with destruction, and he had already entered into the legends of the Legiones Astartes long before the Horus Heresy. At the Conclave of Optera, he renounced his position and departed with Nathaniel Garro, Knight-Errant of Malcador the Sigillite, for Terra, leaving his lieutenants to take command of the Dark Brotherhood and lead it as they saw fit. It is believed his duty to the Sigillite culminated at the Battle of Terra upon the walls of the Imperial Palace during the very climax of the Horus Heresy.
- The Horus Heresy - Book One: Betrayal (Forge World Series) by Alan Bligh, pp. 99, 266
- The Horus Heresy - Book Three: Exterminatus, (Forge World Series) by Alan Bligh (Forge World Series), pp. 82, 162
- The Horus Heresy - Book Five: Tempest (Forge World Series) by Alan Bligh (Forge World Series), pp. 96, 221
- The Horus Heresy - Book Six: Retribution (Forge World Series) by Alan Bligh (Forge World Series), pp. 57, 61, 67, 79, 84, 95, 226-227, 266
- The Horus Heresy - Book Seven: Inferno (Forge World Series) by Alan Bligh (Forge World Series), pg. 81