Mississippian pairs a genuine resource-into-Food economy with an unusually sharp defensive and diplomatic toolkit — a civilization built to grow fast and then hold what it builds.
"Goose Societies" gives all Buildings a Food adjacency bonus for nearby Resources, plus increased Production toward constructing Buildings. Its Antiquity Age Apex tier adds increased Combat Strength for Land Units while defending, and making Peace with another Leader resets your Relationship to Neutral and grants a free Merchant in your Capital — a genuine incentive to end wars rather than let them drag on.
The Watonathi is a unique Merchant unit that earns Gold per Resource acquired when creating a Trade Route. The Burning Arrow is a unique Ranged unit with increased Combat Strength against Fortified Districts and Siege Units, and it applies a Burning status to tiles that damages any unit ending its turn there — a strong area-denial tool against sieges.
The Potkop is a unique Improvement adding Gold, plus extra Food for each adjacent Resource; it must be built on a Flat tile. The associated Wonder, Monks Mound, adds Food and increases Resource Capacity in its city, and must be placed adjacent to a River tile.