User blog comment:B214/Question and Answers 6/@comment-26293136-20161019070650/@comment-10330822-20161021113025

I would say it depends on the power of the devil. Given how some can change their appearance, reincarnate humans depending on their class, most things shouldn't be impossible. Gender swapping seems off limits, but Le Fey is talking like demonic magic is very simple, you imagine what you want and it manifests. That leaves a lot of wiggle room for possible contracts.