Good work
Pretty damn good with the whole terrain, upgrades and overall gameplay though I do recommend that you make it that heroes can be used between games, because a lot of the time when they have reached level 4 and got some decent skills it doesn't really matter since you usually already gained the upper hand on your opponent, also I think you should make it that all legions (Humans, Undead, Steam and Wild) all have their own sea units and even dragons as it seems odd having undead with mermaids or pirate sharks. (Actually then again when was a pirate shark ever normal?)