 The replicators are taking over the galaxy and are killing off the goa uld. The replicators are becoming immune to any attack that is thrown at them. Then a way to destroy them is found: A weapon capable to destroy all life in the galaxy and dialing all the gates in the galaxy at once so that the replicators cannot adapt. The device can be altered to only destroy the replicators. That is why Baal and the real Carter join forces and the awesome battle for the galaxy begins.