The planet is completely covered in ice sheathed desert sand, with oddly formed icebergs and thick layers of gravelly permafrost covering the near entirety of its surface. It is the closest epiphany of absolute zero, not possible in our dimension, where atom's can become so devoid of energy that they stop moving entirely, thus removing the person or object from existence. Solar radiation is the sole source of energy for the planet, which keeps its few inhabitants from dying immediately.
People exiled from the Imperium are sent to Grodeskue, and only the toughest can discover the one portal of refuge: To Earth.
Grodeskue was discovered during the Imperialis dynasty' expansion across the Nether-verse, and was simply dubbed an external territory and as such was left uncolonized and relatively uncharted. At the time, numerous prisoners were taken during the seizure of planets fighting against the dynasty, and crime was abundant in the anarchy that ensued immediately before the Imperium annexed its new territories.
The need for a prison planet was evident; A system of normal prisons would be a waste of expenditure, and so a search was undertaken for a planet to house the prisoners until they could be brought to trial. In all honesty, the Imperialisi wanted their enemies removed, and such found the most hostile environments possible. The worst of them all was Grodeskue, where the intense exposure to the coldness of space and the solar radiation that bombards the planet with its unyielding onslaught could easily kill even the toughest of the Imperialisi in only a day. Regular transports sent billions to their deaths over the centuries of solidifying the Imperium, and eventually it was left uninhabited but still used to exile enemies of the dynasty.