I had the idea of a trap which were gargoyles that could be placed ontop of your walls. The gargoyles would be a one time use trap and would cost dark elixir. They would resemble a dragon but its stats would be scaled down. The gargoyles would be built out of the same material as the wall it was placed on. And the more upgraded the wall the better the gargoyles stats would be. It would have a radius about double the air mines.