The Hagilur System
The Hagilur system is located deep within a dead-zone of space with no other celestial bodies around for millions of light years. This alone would have ensured it to be a pretty desolate place to inhabit but the unstable nature of it's binary stars guaranteed that life never managed to gain a foothold in this sector of space. The pair of red super giants that illuminate this system go through continual cycles of one star cannibalising mass off of the smaller brother before going nova and reversing the process. This periodic ejection of mass and radiation bombards the surfaces of all the surrounding planets scorching them of any potential to harbour life but at the same time creating a layer of crust incredibly rich in exotic nuclei useful for powering the furnaces of the Imperium and providing high quality plasma fuel.
Hagilur 4-6 (5)
When the Imperium first explored this system it was evident that due to the high levels of radiation given off by the star pair even when they weren't going nova, that settling a mining colony here would be all but impossible. It was even dangerous for the explorator ships to venture too close into the system away from their deep space orbits but, never the less, it was decided that the planets should be catalogued. During this systematic study of the orbiting bodies and their classification the discovery of Hagilur 4-6 occurred (although back then it was erroneously dubbed Hagilur 5). Hagilur 4-6 is unique in the system as it is completely locked in the shadow of its parent planet, hence its original mistaken identity as the 5th planet. This bestows it with a incredibly harsh, frozen climate of permanent night but most importantly of all utterly shields it from all the radiation (apart from the neutrinos obv.). Immediately the possibility to use this as a base of mining operations was realised and soon the attentions of the entire fleet was turned to finding a safe passage to the moon for future colonists.