Trap Walls

Basis: Trap Walls look and level exactly the same as regular walls, except when you destroy them, a poison spell is released! As wall levels increase poison radius/effect increases as well! The defending base sees the walls with a flag marker or perhaps sees the walls inverted in color, but the attacker can't tell the difference!
When it comes to max number of walls I think somewhere around 6 by th11 would be appropriate. Running into a trap wall line wouldn't be all that dissimilar to hitting a tesla farm.

already ruled out