This is a story I thought of a while back, but now I think it might work well with the game.
The universe is full of life. there are many interactions between many planets, all sharing their cultures and working together to prevent tyranny and other nasty things from happening. at the center of this is the Nagarians; a wise and highly intelligent race with a very powerful conscience. they have been able to advance their technology far beyond any other race. Soon, they discover how to transfer one's consciousness into a machine. since this will allow them to live centuries longer than their regular lifetimes, and they share their technology without expecting payment, many people use it before they discover a vital secret: in the process of turning into a computer makes them lose their conscience. These new computer beings see all intelligent life as a threat and competition, and using their advanced technology begin to wipe all life from the universe, acting through any robots connected to their network and later through devices specifically designed for their purpose. now, the only living beings are those that live alone in small ships or those that have hidden in planets far underground. or, perhaps the players are those who have perfected the computer transition technology, and are now living inside robots with whole minds.