The theme of this map was the idea of using the "river" tile to create vast swaths of "swampland" rather than the more typical narrow rivers. Dry land routes to each player's base are available, but to secure most of the resources and production on the map, you will have to get very used to swamp combat!
Amphibians are the obvious choice for controlling the map, since they aren't slowed down by swampland and in fact deal critical hits while standing in it, but only two of the four major swamp regoins are easily accesible by said amphibians - and the other two have the boon of towers for aerial units, another strong choice for swamp dominance. Spearmen are far less useful since they're reduced to only moving 1 tile per turn in the swamp, and the wagons that would normally speed them along can't penetrate the muck at all!
