Civilization V's first expansion is out next week. Gods & Kings most notably introduces religion (gods), new civilizations (kings), and espionage (&?). I'm optimistic about the new systems, which you can read about in my recent hands-on preview (opens in new tab) , but for an overview of the new leaders and units, hop inside to watch Producer Dennis Shirk and Lead Designer Ed Beach talk to someone standing next to the camera.
Neither of them mentioned Sweden, which is madness. Gustavus Adolphus (opens in new tab) , I choose you!