Star Trek meets the Greys
It's and Idea I've had floating a round for a while for a threat to be used during any era. The basic concept is this:
1. Let's take all of the legends/stories of 'Grey Visitors' and make them at least somewhat accurate
2. Let's make them at indifferent, possibly malevolent, to Sophont (most humanoid) suffering while they go about their business. None of that 'Space Brothers' nonsense.
3. Feed the motivations over dribs and drabs, but keep it...erm...Grey for the players.
4. Their technology, while in advance of Alpha quadrant, is still comprehensible, just exceptionally difficult to scan, and the thinking process in using it properly should be challenging (think Darmok, but expanded to using the tech).
5. They tend to keep test subjects around for a long period of time. Wither or not the subjects are still stable is open to question....
I'm thinking of generating scenarios for ideas, but would not mind a sounding board
A brave little theory, and actually quite coherent for a system of five or seven dimensions -- if only we lived in one.
Academician Prokhor Zakharov, "Now We Are Alone"