Underground troop?

I always had this idea of what if there was a troop like a worm or tremor/drilling monster troop that attacked under ground or dug holes in ground to go under walls and come up inside base to attack. Only problem is either it has to be expensive to ave one or to even get one to use, because it seems untouchable if it doesnt need to break walks. But it would be vulnerable until it gets inside base where cannons and stuff can attack it.

I think it would be a very good idea, as a distraction though. I think it should have high hitpoints(2500) but low damage(40) and it would be 25 housing spaces. It would be used as a distraction so the other troops can attack in peace.