At the time of its integration into the Imperium in the the 36th Millennium, Gamede III was a lushly vegetated feral world, it's populating consisting exclusively of primitive tribesmen to a select portion of whom the tenacious and uncompromising attentions had contrived to convert to the Cult Imperialis. However, a fairly considerable portion of the tribal population remained stubbornly pagan, refusing to submit to the Imperial Creed. Ultimately, the Missionaria Galaxia established an Imperial-grade and technologically outfitted cathedral near to the geographic centre of the most densely populated of the tribal lands, in the Adrathi Lowlands, so as to better centralize the conversion efforts of the Ministorum and to establish a permanent source of contact between the planetary missionaries and the Imperium.
In 434 M39, this fairly mild state of affairs changed drastically and direly. On the agr-world of Antar IV, 80% of the planetary population rebelled against the Imperium, including the Governor and virtually the entirety of the PDF, and eliminated all of the Arbites and Administratum adepts assigned to the planet in a matter of hours. When the 18th Kelvoran Dragoons Regiment arrived to pacify the planet, it was immediately intercepted by a considerable fleet of both Antaran PDF system vessels in conjunction with a number of other ships of unidentified or inexplicable nature, including several system ships from other regions of the sector, somehow able to reach the world despite the fact that they were supposed to lack both Warp Drives and Navigators as part of their particular intended role. But the most shocking event that of sordid day was the disgrace that the distinguished and veteran Kelvorans suffered as several of their own platoons turned upon their brothers as the Imperial Navy vessels they were transported upon were boarded by the overwhelming numbers of the foe. Before they could even adjust bearing, the vessels of the Imperial Navy present were obliterated, their plasma reactors overloaded by saboteurs and their hulls pummeled into oblivion by multiple suicidal broadsides. And alongside them perished the 18th Kelvoran, lost to a man. And with the spark that was this act of treachery, a conflagration of monstrous proportions now swept the sub-sector, dozens upon dozens of worlds revolting almost simultaneously, Regiments collapsing as blood-bonded comrades turned upon eachother, Navy crews mutinying and making off with vessels only to be seen again at the side of the fleets of the traitorus planets, their vessels heretically modified to integrate Warp Drives and equipped with Navigators from a wholly unknown source. Gamede was caught in the middle of this tide of heresy, and enveloped in it wholesale before it could even begin to react. Hundreds of heretical tribes turned against their faithful brethren, and as if to add insult to injury, dozens of Ministorum priests turned with them, corrupted by some unknown, insidious source.
And yet, in this sea of heresy and betrayal, blossomed one of the most vibrant fruits of faith and loyalty. In the Ursaki tribe, one of the few tribes in the lush tropical forests of the Leyl region to convert to the Imperial Creed, arose a war-chief known to the peoples of the Leyl as Sary Kaetar, but to the Imperium as the Saint Seryilla the Sublime. When the previous war-chief, Arzan Netys, declared for the Shar Terla (an enormous regional alliance composed of the majority of heretical tribes in the area), Seryilla strode forth from among the ranks of the warriors assembled to hear his declaration and decapitated him, a seasoned warrior of over a hundred battles, with a single stroke of her axe. And when Seryilla, who was but a novitiate warrior with no true experience with combat or leadership, immediately declared herself War-Chief in the name of the God-Emperor, she was meant with cheers of joy and submission by warriors who, moments before, had been lauding the betrayal of the Imperial faith and grinding their axes and sharpening their spears for war against the Ministorum and its paltry allies. And, days later, the tribe, which had been wavering on the brink of heresy and rebellion for the best of a decade as a result of heated disputes over dogma and territory with the Missionaria Galactica, immediately declared war on the Shar Terla and all others taking arms against the Imperium, condemning them for their constant heresy and insufferable heresies. The tribe of Seryilla soon stormed across the plains and jungles, ambushing and destroying dozens of heretical warbands, until the Shar Terla finally descended upon them in force. On the fields of Kzytar did the combined armies of Shar Terla, over twenty thousand strong, meet Seryilla’s isolated warband of eight hundred men and women. And on those same fields was won one of the most stunning victories known to Imperial military historians, Seryilla’s forces routing over twenty times their number in a single day of brutal battle, the future Saint leading the very tip of the charge, bellowing prayers of vengeance and contempt, cowing all before her into terror and submission, breaking the back of the Shar Terla. So it came as something of surprise for her tribesmen when the fanatical and brutally uncompromising warrior-woman offered to spare the life of any Shar Terla that agreed to renounce their heresy and commit themselves to the Emperor in contrition. It came as even more of a surprise when every single Shar Terla captured, over three thousand, submitted to the mercy of the Emperor and Seryilla on the spot.