I'm not quite sure this is beneficial enough to warrant an ability cost at all. In fact, I think the ability itself is underpowered. I'm not quite sure how to turn it into a great ability, because all I can think of is a mini Millstone effect, removing the top card of your opponent's deck instead of revealing it. Of course, this is probably a bit too powerful (every time this has been suggested it has been shot down). Just a thought.