Ok, How about a troll that burrows under walls and blows up defenses on the other side? Here's the cool part, the damage is different depending on what structure gets hit and how it affects the surrounding areas. Real Wars have had this kind of burrow and blast stuff historically, it would be good to bring this unpredictable new wrinkle to the game. I can picture now people's reaction of joy or disappointment depending on what kinda damage occurred inside the walls. Troll placement would be key in determining good results.

