The Kamenka Troika is the collective name for the three satellite worlds of the planet Kamenka Ulizarna, an Adeptus Mechanicus fiefdom. The Troika is mentioned in Imperial records as being freed of a Greenskin infestation during the middle years of the Great Crusade.
The Imperial forces tasked with exterminating the xenos breed were the Thousand Sons Legiones Astartes, Legio Astorum of the Titan Legions and a unit of the PanPac Eugenians of the Imperial Army. This tasking was issued by the Emperor himself, and proved a difficult one for all involved. The campaign took two years to complete and caused significant Imperial casualties, including almost an entire Fellowship of the Thousand Sons and also the entirety of the Legio Astorum forces.
The aftermath of the campaign is significant in two ways. First of all, the Thousand Sons decided to honour Legio Astorum by recovering the wreck of the last Astorum Titan to fall, Canis Vertex, repairing and transporting her to Prospero to mount upon the pyramid of the Pyrae Cult. Canis Vertex would walk once more about a century later, during the Burning of Prospero. Secondly, the loss of one of their Fellowships was never made good; Magnus the Red decided that the reduction of his legion from ten elements to nine was a significant moment, and the legion was reorganised into the Pesedjet as a result.
The actual geography of the Kamenka Troika and their current conditions are unknown.