Absolutly nothin'!
In my opinion fog of war adds nothing to this game aside possibly from Regulus setting up a mine field. There might be some strategical aspect to The Rook erecting towers, but being on a timer, doesn't strike me as an agrument for fog of war.
There arn't many RTS'y plans you need to keep hidden in Demigod and recently I feel the fog of war a nusance. It feels as if fog of war was implimented into an RTS system that didn't work and it's been kept for tradtion or some other reason.
Am I overlooking some reason to keep fog of war in the game?
I suggest making fog of war to be default off.