I could see at least 2 directions for the needleplay: 1) contemporary AU with alternative!Morgause and Morgana as the younger sister who's trying to act as old & cool, and so they do the piercings at home; or 2) any era with play piercings, with or without magic (with magic it could be a great test of your control in levitating objects; without maybe as an exercise in trust, or Morgana showing she's willing to withstand pain to go through with their plan).
Personally I find the idea of play piercings hotter, because you can arrange them for visual appeal in combination, put them in areas of skin where a piercing wouldn't stay longterm, and because there's the whole pain-play aspect. Plus I saw a play piercing scene with two very hot ladies at a lesbian BDSM night years ago, and still vividly remember the neat line of horizontal needles and trickle of blood. I suppose part of the appeal is the crazy amount of trust involved - trust from the person being pierced, but also the piercer trusting themself because you could so easily transmit diseases if you were careless.
no subject
Personally I find the idea of play piercings hotter, because you can arrange them for visual appeal in combination, put them in areas of skin where a piercing wouldn't stay longterm, and because there's the whole pain-play aspect. Plus I saw a play piercing scene with two very hot ladies at a lesbian BDSM night years ago, and still vividly remember the neat line of horizontal needles and trickle of blood. I suppose part of the appeal is the crazy amount of trust involved - trust from the person being pierced, but also the piercer trusting themself because you could so easily transmit diseases if you were careless.