User blog comment:AdvancedRookie/Saddest Game Moment?/@comment-2049397-20100508181244

It was an OSCP mod for FreeSpace2, when after the main campaign, they find a Derelict Shivan ship, research it, the ship breaks away, because it turns out it still had Shivans in it, and a Massive invasion fleet jumps out of SubSpace.

And in the ending of the campaign, they find out that the Shivans who have just throwing around the Allied Fleet, like they were in the way, never meant to cause a 3rd invasion, but they were just.....going home.