Master of Orion II: Battle at Antares

Master of Orion II: Battle at Antares is a 4X turn-based strategy game set in space, designed by Steve Barcia and Ken Burd, and developed by Simtex. Long before the time in which the game is set, two extremely powerful races, the Orions and the Antarans, fought a war that devastated most of the galaxy. The victorious Orions, rather than exterminate the Antarans, imprisoned them in a pocket dimension before departing the galaxy, leaving behind a very powerful robotic warship, the Guardian, to protect their homeworld. Some time after the game starts, the Antarans, having broken out of their prison dimension, begin to send increasingly powerful fleets against the players' colonies, to destroy them along with any defending ships, before they disappear back to their mysterious realm.