Quoting Gammit10, reply 94
Because I am such a visual person, I would most prefer to see the faction differentiation. To alter the cities or surrounding land for each faction would be awesome. While the kingdom versus empire land and building differences are already a start, I would ideally like to see some differentiation in the city's buildings.
You're going to get both. SEE and PLAY.
For...example...ONE of the faction gains population by defeating people on the battlefield. That is, non-champions who fall on the battlefield (who are sentient) become slaves and are added to their population.
Another faction can claim land via magic rather than having to build outposts.
We''re not looking to pepper each faction with a hundred little things but rather have a handful of big obvious things.
This is excellent news!
I agree with the "handful of big obvious things" approach. This will likely be easier for you to balance, and yet it will provide enough difference in playstyle to encourage experimenting with other factions.
I would like to second the "surrounding land" idea that Gammit10 put forward. One faction should spread the frost tileset, another the swamp tileset, yet another the dark forest tileset, etc. The spreading tilesets should also carry a benefit for the faction involved.
For example, one faction might get warg/wolf troops as a percentage chance based on the total area that they have covered with the frost tileset (much like the eco-hippie factions from Sid Meier's Alpha Centauri). The swamp faction should gain the ability to get increased movement in swamps (+1 movement across swamp tiles) making the swamp a type of "road" for that faction.
I really like the "population gained as a result of killing" idea.
Perhaps a faction should gain a bonus based on the number of forests surrounding their city (ie. increased production per city, increased unit defense in forests and +1 mana for every forest tile traversed by a champion or sovereign (maximum "X" per turn to prevent spamming) as well as gain a faction specific spell: raise forest.