MArcomage

We have 25 wall and 30 tower in normal game. And this card destroys starting wall and does 4 dmg to tower for 2 bricks - cheapest resource in game. It's too much, i think. Even the fact that it's useless if enemy wall less than 18 doesn't mean anything. Use it and 2-3 attack cards. You win.
Remove damage if wall>18.

I don't understand your calculation... If I'll play it as the first card, the result is enemy wall 19 and my wall 12...

Oh, sorry. Misreading.
But it would be totally ineffective. You do damage to enemy, even more damage to yourself and pay for it. Not much but still pay.

I see this as being a cheap finisher to go for Gentle Touch or as a throwaway to gain Unliving tokens when the player's wall isn't high enough to cause the reduction.

That being said, I don't think I'd use it.

can be tweaked a bit but as an offensive card sacraficing some wall to do damage is awesomesauce against tower builders?

EDIT: made is stronger for you naysayers (i'd still use old one)

old one:
If wall>18 wall -18, attack 11
else attack 2

I think something like:

wall -18, attack 11

Would be more interesting (i.e. remove the wall requirement). This would make it great against pure building decks, since you could run your own wall down to 0 and continue getting the 11 attack cheaply. However, it would be putting yourself in extreme danger if the opponent has any offensive aspect to his deck.

That give me an idea for a card - to do more damage if your wall is destroyed. Or something similar to Berserker but based on wall.