Belaxalar Xenocide

The Belaxalar Xenocide was a xenocidal purgation campaign conducted by the Castigators Space Marine Chapter's 2nd Company against the alien Belax xenophorms. The Adeptus Mechanicus coveted the natural resources of this world, and so, at the behest of their Chapter Master, the 2nd Company launched a xenocidal campaign upon the world of Belax and eradicated it's population. Following this campaign they handed over the conquered world to the Adeptus Mechanicus to do with it, as they will.

History
The world of Belax was stark, with an atmosphere high in gaseous ammonia and low in oxygen. Elaborate crystalline cities dominated the landscape, inhabited by the Belax, a young and belligerent race with advanced technologies. The Belax utilised birthing chambers, fluid-filled tanks that could hasten the development of the young. The technology had even been used to improve upon their anatomy, breeding warriors with armour plates, poison sacs, spiked knuckles and other such martial modifications. Vicious wars between the nation-states of Belax were not uncommon; indeed the only thing capable of uniting the disparate peoples of the Belaxalar would be an Imperial invasion.

Captain Caphius, at the behest of Chapter Master Avitus, conducted a xenocidal campaign against Belax so that the Adeptus Mechanicus could conduct mining operations upon it. The 2nd Company fought a ferocious war against the Belax, before emerging victorious. By the time the 2nd Company left Belaxalar, all of the Belax had been utterly wiped out. The Adeptus Mechanicus abandoned the world less than a decade later, after finding that the ore extracted from the planet was not of sufficient quality to merit excavation.