I’ve finally got a definite idea for the campaign world using d12 rules. It’s going to be about exploration of recently rediscovered Dyson sphere, more specifically Dyson shell. I’ve stated that the game is going to be space opera (among other things) so hard science can take back seat and I can do cool stuff based on concept.
Basic idea is that The Guild has discovered a lost Dyson sphere world and has invited all different factions to participate in its exploration. The Guild is of course interested solely in profit and control of interstellar flight and trade while other factions have their own motivations.
The Dyson sphere was built to be a paradise world and giant lab by the previous human civilization that was lost in wars long forgotten with enemies unknown. This of course means that there is lots of strange stuff waiting for someone to find it.
Enter greedy, ambitious, trigger happy explorers (i.e. player characters) supported by various factions and the game should roll with its own weight.