[ Mirajane thinks for a long moment before leaning back to Erza's ear. She bites it, but after a few moments of that, she speaks up. ]

I know what I want. I want you...Erza, dig deep. Dig deep and tell me the worst, most horrible thing you want done to you. I'll use all the powers at my disposal to make you regret it.

[ Besides, there is no better punishment than forcing Erza to say something shameful at the expense of her dignity. Or what little she has left, given the current situation. ]