Oh, I can do that myself. Just did, in fact. I was hoping for something more convenient...
1. It's instantaneous, like using a Fire Bolt. When the Enchantress uses her ability, the damage of the target creature is instantly inflicted against the opponent, and then on the opponent's turn, the creature can still attack you normally. I figured "controlling" the creature with a renewable ability was a bit OP. This is only intended to punish an opponent for playing a creature with high attack, not to lock something out.2. I'm using http://helltgivre.free.fr/elements/card.html to make these cards. I will totally love you if you tell me how to do that with it!
I do hope it can't be used in combination with Cremation, as that would be too devastating.
I love a lot of the scenarios that people have identified, such as in conjunction with gravity pull.