MArcomage

This should have an additional effect like: "If new, enemy wall -5, enemy tower -3."

I disagree. I'm pretty sure the entire point is to set up use of the Destruction keyword, and it seems well balanced at that without its own effect.

I think the card should have some effect of its own. Maybe have it like a reversed Alchemy: enemy bricks and recruits -2. Or a negative effect that effects both players damaging stock, wall, facilities, or production.

Or how about something that targets buildings or nature like mold does:

Discard all + Tower and/or Nature cards from the game
Procuction X0
Stock +N
N= Number of cards discarded.

Cost would be increased of course.