More likely than not Merlin will once again assault some fortifications, like the Golden Palace or Black Fortress of mr2. Might I suggest elevation changes, ex. a castle on a cliff? The higher elevation results in less accuracy when attacking from below, making Merlin's job harder and more realistic. Also, I would like to see walls. There can be different types, such as wooden palisades or fortified stone walls, each with different damage absorption capabilities. The walls will block any blasts not of a ballistic origin (aka arrows and the like) and take damage until they are destroyed, letting forces flow through the breach. Perhaps, once Merlin kills all the enemies, all of the walls will fall automatically, because they clearly cannot attack back.