A part of the current Steam strategy fest is the indie game “Theocracy”. Theocracy is an old-school turnbased 4X game, heavily inspired by Civ1 and 2, but with a focus on religion and mysticism. So besides expanding your empire, you also need to spread your religion and convert pagans.
The game is currently on sale for 4.89€ instead of 6.99 until September 4. The developer is also a fellow civ-fanatic, and will answer any questions in the thread dedicated to the Theocracy here.