The players have decided to be a crew of explorers/traders with loose morals, a la Firefly. Only, they don't have a ship. So I sent them on a doomed quest for an unknown patron to salvage an alien ship from some ancient underground ruins on an unaligned world. I used Donjon tools (http://donjon.bin.sh) to generate the ruins as we went and improved the rest. They're on the 2nd floor; not sure how many there are yet.