Very interesting card: very efficient indeed if you both want to destroy a conjuration and create one (not that unlikely!)
It could also interact very brutally with cards that build up tokens before having a dramatic effect: you'd get an interesting dynamic where the owner had to protect such cards against conquering, as well as from the (usually less efficient) attempts to smash them to bits.
How does this interact with walls? If it can target them, do you have to control both sides, or just the one you choose for targetting? If you are allowed I assume you have a nominal target zone and must put your own conjuration there: if you then placed another wall, could you put it on a different side of the same zone? Could you extend it? Some very interesting potential control here if the answers here are 'yes'!