Nifty. Would influence the way people play just by existing.

I wonder how high this is in power level. I'm terrible at evaluating that, but it seems to me like it might be pretty strong.

Eh, weaker than Counterspell, heck; weaker and arguably not even cheaper than Cancel. So not worryingly powerful; though still durn good.

Reminds me of Perplex. This is fewer cards, but much better if the opponent has an empty hand. But "Counter target spell if its controller has no cards in hand" could easily cost .