Was it morally right to use a mind-control spell on Rainbow Dash to turn her into a horny slave who would do anything to please her mistress? Probably not.
Would Twilight get in trouble if someone found out about it? Probably, yes.
Was she going to stop doing it and tell her the truth? Hell no! It all just felt too fucking good to give up like that.

Plus, Rainbow had said she wanted Twilight to dominate her. After she'd already been put under her spell, but the purple alicorn didn't have time to worry about details like that. And if someone caught her? Well, she did want to see what having multiple slaves was like...

Contains mind control, lesbians, femdom, femsub, a dildo, orgasm denial, hypnosis, induced arousal, spanking, hypnotic triggers being used on one of the two, cunnilingus, very very minor bondage, mentions of a harem, sex

Cover is image number 570296 on Derpibooru.