I like the effect, but I don't think it needs two different equip costs. That's the sort of thing that I think only works well if done in a cycle. In any case, I think that this is more powerful than [card]Mask of Memory[/card], but not so much so that it needs the

/{4} cost. It's like a small Yawgmoth's Bargain, in some ways, but it's still dependant on a creature dealing combat damage to an opponent, and, unlike Bargain, can't net you additional cards if the ones you draw don't help you. I think that

/{2} would be aggressive, but not terrible. A low-ish equip cost isn't going to break this, since no matter what, it's only ever going to do anything once a turn, anyhow.