Permia E895500 -3 X
Settled late in the expansion phase of the first empire, Permia was originally an arid garden world, entering a supercontinent glaciation phase, with extensive biomass and diversity. Colonization went normally, and population expanded and spread out particularly along the coasts, focusing on aquaculture. Following the withdrawal and eventual collapse of the empire, permia was well of, having a human habitable environment, and a well developed local society able to easily support tech 7/8. While they were unable to maintain interstellar ships, and only limited insystem ships, they were nonetheless occasionally visited by wantering tramp traders, and had little to interest raiders, especially given their tech/defence abilites (defenders with Jet aircraft, Advanced tanks and nuclear weapons being less far less appealing than neolithic or medieval victims).
In short, while the planet stagnated economically, and had to tool down from even imperial standard tech for colonies, they did quite well. eventually, as the long night progressed, contact stopped, at least partly due to the yadda yadda blockade of techtech in the name name wars, and Permia settled into the easy life of a sleepy forgotten backwater planet, with the last recorded stats being 885786. x hundred years later, Permia was rediscovered, and was initially not even connected with the original records. Initial assessment showed an atmosphere of type 9, with extremely high levels of CO2, SO2 and particulate pollution. the ocean wasalmost entirely anoxic and poisoned by rotting organic mass. Glaciation had dropped to 10% of its original level, and the planets temperature had risen by at least 10 degrees (Imperial). The biomass indications were almost nill. Massive volcanic activity was found in the northern hemisphere and the atmosphere was practially opaque, with a low level but significant and increasing greenhouse effect .
At some point during the long night the planet as a whole had essentially died. Gradually across the last few hundred years, at least 80% of all multicellular life on the planet became extinct, including almost all marine life from plankton on up, causing an almost total collapse in the oxygen cycle; oxygen concentration at coast levels was equivalent to that found at 10,000' on Terra. 70-80% of all land based life was extinct, including most large forest areas. The coasts and landscape are choked with slowly decomposing corpses and rotting vegetation; the air is foul and thin, and the planet shrouded in almost perpetual murky twilight. The population has dwindled along with the planet, and now numbers at most seven or eight hundred thousand, mostly nomads in the arid inland areas, or semi-urban populations within the collapsed and largely ruined original coastal cities. Many areas of the continent are entirely isolated by highlands that are now uncrossable due to lowered oxygen content. Government is entirely local, and largely tribal, and extremely prone to conflict. Tech has regressed to pre industrial levels, with high points being weaponry and filter production.
Initial investigation as to the cause of the collapse centers around the massive volcanic traps in the northern part of the supercontinent. Covering hundreds of thousands of square miles, the lavafields appear to have erupted at least partially under an extensively glaciated area. the effects of the volcanic activity were twofold -first, massive emissions of CO2 and So2, as well as ashfall and suspended particulate swamped the atmosphere, secondly, the massive melt of the glaciers flooded the coastal areas with cold fresh water, essentially killing off the coastal marine envirnoment, beginning the O2 collapse. Significantly, the CO2 also acted to poison the remaining waters, and the collapse of the weather systems began destroying the land based ecosystems along with the pollutants.The final stress occurred as the glacial melt was exhausted, and the local waters began heating up and melting frozen methane beds on the largely dead ocean floors, releasing vast amounts of methane into the water and the atmosphere, causing the final death of most of the O2 producing biota.
The animal population was already somewhat stressed due to adaptive changes caused by the glaciation, and the sudden heating and climate shifts was devastating. Unlike many extinction events, the dropping O2 levels caused large active omnivore/carnivore animals with powerful circulatory and respiration systems to preferentially survive longer than many others .
The surviving population is considered for relocation, but is currently far to hostile and xenophobic to contact, and additionally, extremely hard to locate due to the their dispersal, and the atmospheric conditions; too, the unbalanced current land ecosystem is also highly competitive and dangerous, and has made setting up a local base at sea level extremely difficult . Currently, contact is supported through a small base on a highland plateau in near complete anoxic conditions.
In case anyone is curious, this is my swords and sorcery setting I'm considering running. Plus, its possibly the most realistic of the hellworlds I've described -its earth at the end of the Permian era, at the climax of the greatest extinction event ever. Well, except for the people. Those I added. Dead seas, and near toxic greenish skies; country sized volcanic fields. Dead things everywhere. Fun.
No cannibals this time, due to the easy access to carrion and fungus... 
o
