Concordia Venus includes new personality cards with the goddess Venus allowing for new strategies, two maps (Hellas/Ionium) on which to play (using components from the Concordia base game in addition to new cards), and rules that enable teams of two players to play against one another.
Note: This listing is for the Concordia Venus expansion; the standalone version of Concordia Venus can be found here. The standalone version includes more maps (Imperium/Cyprus in addition to Hellas/Ionium) than this expansion does (because the base game already includes Imperium, and Cyprus is available as part of Concordia: Balearica / Cyprus.