A cold, unwelcoming and low-tech planet, consisting of dark forests, ice-capped mountains and bleak plains. Purgatorians lived in simple, isolated settlements consisting of ground hugging low-tech dwellings. The economic mainstay was mining. It had a single spaceport and a detatchment of Cadians for protection. Legends told by older races such as the eldar had spoken of a devastatingly powerful weapon known as the "Hand of Darkness" buried within the substance of purgatory. It was said to have been transported directly from the warp and buried a very long time ago when the galaxy was very young. The inquisition had long been attempting to divine its purpose and position but to no avail.
One summer, a sudden and devastatingly effective surprise raid by Chaos spacemarines over-whelmed the local militia and the Cadian detachment, the defenders being massacred horrendously. By the time the ultramarine relief force accompanied by Inquisitor Horstarrived, the Chaos spacemarines were long gone. Psychic divination also revealed that the "hand of darkness" had also been removed. The Gothic wars were looming.
(Ref: Codex Chaos, 2nd Ed, Page 49)