The Geonide Crusade was an action taken by the Black Templars Space Marine Chapter intended to preserve important Imperial technology, scientific research and Adeptus Mechanicus personnel from a Chaos-inspired rebellion on the planet Geonide. The Forge World of Geonide was an Imperial planet worthy of note due to the scientific research being conducted within the mile-high laboratory facilities that dotted the planet's surface. The brilliant minds of Adeptus Mechanicus Tech-priests worked feverishly upon such important projects as new propulsion drives for the Imperial Navy's starships and the latest laser technologies. Then there were the classified projects involving artefacts and relics of bygone eras. Whatever the work, all is done with the interest of furthering the cause of the Emperor. However, underlying all this approved research was the possibility that someone might dig into heretical subjects outside the strict boundaries of knowledge set by the Imperium.
Open rebellion against Imperial authority in Geonide's major cities erupted without warning, taking a heavy toll on the populace and priceless research facilities. Before long, the true cancer behind the unrest was revealed to be a newly formed coven of latent psykers tainted by the corruption of Chaos. These rogue psykers had been manipulated by Chaos Sorcerers into unleashing the unholy energies of ancient Warp-Drives stored on the Forge World to open a rift into the Immaterium. This allowed the Taint of Chaos to infect most of the planet's population, and the soon mostly insane and mutated citizens of Geonide proved very difficult for the remaining Imperial defenders to contain. Within a year, over 75% of the planet's population had fallen to the corruption of Chaos.
The Geonide CrusadeEdit
Assistance for the remaining uncorrupted defenders of Geonide arrived in the form of a Black Templars Crusade fleet. After many valiant efforts to reclaim the planet on behalf of the Space Marines failed as simply too much of the planet's population now served Chaos, an Exterminatus was called for and ultimately carried out by the agents of the Inquisition, who had been present from the beginning of the rebellion. However, the Inquisition held their fire while a group of brave Black Templar Astartes ventured to the planet's surface to retrieve invaluable Mechanicus artefacts, research documents and important Imperial personnel from being swallowed by the rage of the Ruinous Powers forever.
As soon as this mission was completed, the Inquisition charged the cannons of their mighty starship and unleashed a cleansing Exterminatus action that utterly destroyed the planet.