Outpost of Tydor

The beings that settled the world of Tydor were refugees, the last of their kind. Survivors of a civil war turned to slaughter, they wanted only peace.

A small world, orbiting a vibrant sun, they brought life to their new world, turning it green by hand and machine.

It wasn't beautiful by any means, but it was home to them, and perhaps they judged its beauty by a different measure, for they would always speak fondly of it when travelling.

And yet, it was only the space of a single trader vessel when all fell to terrible ruin. What one trader left as a unremarkable, though pleasant world, the next arrived to find as a lifeless husk, shrouded in a mist that would not depart, its oceans gone and all life vanished.

And it was vanished. Not a cell remained, all gone. Even the depths, heavy with mist, once home to the oceans of Tydor, were floored by dry rock, untouched by life.

The creepy thing was, the cities still stood undamaged, their power run down, the wind howling through the towers.
And yet, not silence enough, for as more than one visitor can attest, one gets the feeling of being watched, one hears... things... machinelike, and clumsy, but when you look, it's all gone quiet.

Resettlement attempts were small, made by travelling Tydorians who had avoided the fate of their kinsmen.
Three efforts were made across the planet, with vast terraforming machines brought to bear on the world, giving it back its oceans, making it habitable for life again, and the colonists made their efforts immediately following.
The terraformers in orbit woke day immediately following the colonist landings to find the landed groups gone without a trace, all that was left was metal and rock.
Even the oceans were bubbling their last, the mists blanketing the world were even thicker than before.

A superstitious breed, they declared the world cursed and abandoned it for another world in the same system, a world still in the process of being turned green.

Tydor's air is thin now, nearly too thin to breathe. The mists still, inexplicably, cover the world. Scholars theorise that whatever has happened there is a result of the mists.

Investigative attempts usually end poorly. Only a fool stays on Tydor overlong, and the bigger the investigation, the more likely it won't return at all, instead suffering the same fate as that which befell the colonists.

The surface is littered with the ships of the authorities, of pirates, and of over-adventurous tourists. The Tydorians have a system in orbit to warn away those who would come near, but it is often ignored by the foolhardy.

GM Notes

Suggestions for the true story:
Ancient plague: The Tydorians were digging deep, and found a relic from a hitherto unknown race.
A whole lab of them, in fact. Twas curiosity that killed the cat in this case, as one of the relics contained a deadly sample of an organics devouring plague, only active at night, engineered to claim its victims in their sleep. This plague has devoured the people, their food, their crops, the seeds in the ground, and the bones in the graveyard, and even most of itself.
The speed of its feeding required use of the hydrosphere, turning the liquid water to mists.
As of now, it sustains and is sustained by the mists, where it drifts, largely in stasis, waiting for skin contact.
Most explorers routinely use protection suits in these sorts of environments, nevertheless, overzealous exploration invites disaster, and the plague acts quickly upon the flesh of the unprepared.

Terraforming Goo: An ancient terraforming technology was awakened by the Tydorians' activities. Using all available resources, it is attempting to create an ecosphere to sustain its long dead creators, going dormant when it runs out of materials.
As dangerous as it has been for the Tydorians, this sort of technology could be invaluable for future terraforming plans amongst all the sentient races.

Suggestions for what it is that's still out there:
Protection robots: Sentinel droids, programmed to protect areas, capable of self-sustaining their energy sources for centuries, they nonetheless must make their area sweeps as scheduled, returning to a low energy stasis state between sweeps.

Terraforming process: The nanite goo is building larger machines for more complex purposes. These machines are unnoticable, and largely unpowered as of yet, but the process can make some noise.

Plot Hooks
Retrieval: Somebody who disappeared there had an item of some importance, and somebody is willing to pay to get it back.

Dying Tydorian: A Tydorian survivor wants to know what happened to his family, and wants to employee the players to find out once and for all.

Crashed vessel: The characters have made a forced landing on the world, and have to find a working vessel to get off.