Ghenna Massacre

The Ghenna Massacre, known formally as the Second Compliance of Ghenna and the Ghenna Scouring, was was an infamous campaign conducted by the then-Loyalist World Eaters Legion against the world of Ghenna, where the entire planet's population was butchered in a single night of bloodshed. In the aftermath of this slaughter, the World Eaters were formally censured by the Emperor and commanded to cease the implantation of the Butcher's Nails cortical implants. But Primarch Angron would pay little heed to the Emperor's dictates and ordered the work of his Legion's Techmarines and Apothecaries to continue with the mass production and implantation of the deadly neural cortical implants known as the Butcher's Nails in all of his sons. This infamous campaign would herald the inevitable fall and eventual damnation of the World Eaters.

History
Gehenna was an isolated world that had endured the horrors of Old Night. Their society was fairly advanced, but unfortunately, they were overcome with genetic diseases. By the time of the Great Crusade, there were less than a thousand Gehennans that remained, kept alive in life-pods. When this world, classified as Ninety-Three Fifteen, was re-discovered by the Imperium, they initially accepted Imperial rule peacefully. But after several years of Imperial occupation, they rebelled. The World Eaters were tasked with retaking the upstart world. Following unsuccessful negotiations with Ghennan emissaries, and their subsequent slaughter upon the World Eaters' discovery of the Ghennan's use of modified artificial humanoid forms and an apparent form of "Abominable Intelligence", Ghenna was officially sanctioned by the Imperium for conquest.

Angron ordered a hasty invasion of the planet, and per the Primarch's newly instilled tradition, the Red Angel demanded the world be subjugated within 31 hours (a standard Nucerian day). Failure to do so would result in the draconian punishment known as decimation, should they fail, with 1 in every 10 World Eaters Legionary being executed for their failure by his other nine brothers. However, due to poor planning, a hastily executed landing and inadequate orbital, heavy armour and artillery support, the World Eaters faced massive resistance from billions of artificial Ghennan "Simulacrum", which overwhelmed the World Eaters Legionaries through sheer weight of numbers. Commanded by Centurion Mago of the 18th Company, the World Eaters commander was desperate to meet the allotted time-frame, so as to avoid yet another decimation in a series of previous ones that had taken place. He was desperate to avoid yet another massacre of his fellow Legionary brothers. Finally receiving adequate heavy armour and artillery, just as the World Eaters forced a breach and broke their way inside the confines of the main Ghenna city, the World Eaters once again failed to meet their Primarch's allotted time-frame of 31 hours to subjugate the planet.

Forced to withdraw their forces, the warriors of the XIIth Legion withdrew and were forced to journey back aboard their Primarch's flagship, the Conqueror, to face their draconian punishment. Angron ordered yet another round of decimation to be carried out, however, Centurion Mago refused his gene-sire's orders. The Centurion's refusal initially amused the Primarch, who then callously ordered Mago to personally carry out the decimation and murder of his longtime comrade, Salicar. When Mago refused the Primarch a second time, this sent Angron into a blind rage, who then proceeded to murder a large swathe of his own sons. The World Eaters Librarians, under Lectio Primus Vorias, subdued the enraged Primarch utilising their combined psychic abilities, putting Angron into an unconscious state, though several died in the attempt. However, Angron would not wake from his slumber, and soon, a crisis erupted within the World Eaters over what actions should be taken. During this time of instability, Apothecary Gahlan Surlak announced that he had created a stable method of implanting the Butcher's Nails implants by reverse-engineering Ghennan technology. They could now implant these archaeotech devices into the warriors throughout the Legion, per their Primarch's orders. Centurion Mago was horrified by the prospect of being a part of a Legion of murderers enraged by these diabolical implants, and began to plot with other original Terran War Hounds veterans to halt Surlak's plans.

Mago would subsequently make an appeal to Centurion Kharn, pleading with him to reverse the direction their Legion was taking, however, his call for change fell on deaf ears. This forced Mago to take more drastic measures, and soon, he gathered other disenchanted World Eaters that were loyal to him aboard the Frigate, Hound's Tooth. Together, they plotted to destroy Apothecary Surlak's equipment before he could fully perfect the Butcher's Nails implants for mass production and implantation. However, this attempt failed, and shortly thereafter, Kharn became the first World Eaters Legionary to be successfully imbued with the Butcher's Nails. With this initial success, Surlak then proceeded a mass induction of 1,000 more fellow World Eaters with the Butcher's Nails. Around this time, Angron awoke from his slumber, and with the Primarch leading these newly enhanced Legionaries, immediately launched a counter-attack against the upstart Ghennans. The World Eaters, enhanced by the deadly Butcher's Nails, slaughtered all those they came across, despite the massive numbers of Simulacrum arrayed against them. Thanks to Surlak's efforts, through his reverse-engineering of Ghennan technology, he was able to localise and pinpoint the command signal's origins of the last living Ghennans in their life-pods. The Ghennans pleaded with the blood-maddened World Eaters to be spared and left alone, but Kharn replied disdainfully that the galaxy belonged to the Imperium and proceeded to massacre them all.

Meanwhile, Mago and his Loyalist conspirators had felt they had no other options left and planned to subdue Angron, Kharn and those World Eaters that had been imbued with the Butcher's Nails, and bring them before the Emperor Himself for judgement. After the massacre of the Ghennans was carried out, the World Eaters on the surface were confronted by Centurion Mago and his Loyalist supporters. They pleaded with their Primarch and Kharn to halt their madness, but once again, their pleas were ignored, and soon, a battle broke out between both factions. During the subsequent fighting Mago was confronted by, and bested, by his former friend Kharn, and before he was beheaded, made a final declaration -- the XIIth Legion would be damned by their actions and the dark path Angron was taking it. The Centurion's final words would later prove to be prophetic. With the death of their commander, the remaining Loyalists halted in mid-battle and submitted themselves for Angron's judgement. With the Legion once again unified, the World Eaters proceeded to scour the surface of Ghenna clean of life, leaving no structure intact and no Ghennan left alive in a single night of monumental bloodshed. It was said that the psychic death screams of the dying were audible to Imperial Astropaths across half the sector.

In the aftermath of this massacre, calls for censure against the World Eaters resounded within the Terran Council. Soon after, Primarch Leman Russ and his Space Wolves Legion were dispatched to Ghenna to confront Angron and his World Eaters and to halt the implantation of the deadly cortical implants.