I’ve watched so many Citadels “making of” trailers full of talk about nothing but walls that I’d completely forgotten that it’s supposed to be a game based on Arthurian legend. For a while it seems as if this fourth part is going to be preoccupied with barriers made from layers of bricks and stonework too, but then the tone switches to Havok physics and heroes. Hurrah.
It seems that the third-party physics may make catapult attacks especially deadly, as the boulder crushes buildings and then rolls around some more over hapless troops. Arrows, too, will behave somewhat realistically (so having a height advantage, perhaps by being on … oh man … a WALL, will be important.)
Arthurian heroes (Merlin and friends) will come to your aid in missions, but only if you unlock them for use by completing side-quests in preceding levels. These will appear in your units and help to lead them to victory.