There are those awesome artifacts in civ 5 BE. They can be obtained from crashed sites, resource pods, quest completion, research focus, or alien nests removal. When combined in set of 3, they will give some extraordinary reward, like some bonus building with no maintenance, like the Drone Command. Or some full empire benefit, like stronger units, cover ops, or city benefits. The patience is the key, gather as many artifacts and make different combinations to see the rewards.