When the light becomes so bright that you cannot see anything but it, it suddenly vanishes. Looking around, you notice that everyone appears to be frozen in time, meaning that this must be how the transformations happen in an instant, yet the person undergoing it always can vividly explain how it happened as if they watched the entire thing step by step.
"Hmm. Yes, you'll do quite nicely" comes a voice from behind you. You turn about and see a woman dressed in an elegant Victorian style, red and gold dress. Her long black hair both framed her head and went down past her thighs, and a pair of fark colored horns are protruding out from her head too. Her black colored eyes with fiery red irises only further confirmed her identity. This woman is a demon.
The women grins and leaps right at you, while her wings appear behind her back and stop her momentum right in front of you. She is taller than you by quite a bit too. She raises a black gloved hand and pokes your forehead with it lightly. She then stands up and smiles. "My name is Nyx, perhaps you know of me?"
"I, don't. I have never met a demon before either" you say nervously.
"What?! Never met a demon... What the hell has happened to your world since I left?" Exclaims Nyx as she begins pacing in front of you. "No, you likely have no clue anyways. Well, I guess I will just have to tag along then. Alright, time to move on with the world again. Oh, and sorry if it isn't to your liking, but you will be given my body, since it contains all of my magical power and my specific abilities which I must have. But in return for this, I will let you be the main personality and will only take over control when either it is absolutely necessary or you offer to switch out with me. And I will teach you everything I know about magic too, which likely is a lot more than you would ever get from some magic school's curriculum."
"I'm sorry, what? I am going to be given your body? What do you mean?"
"You turned 18 did you not? This whole transformation thing is my doing. So as the one in control, I can just give you whatever I want as a transformation. So I am giving you my body, then I will possess you as well, so that we will share my body. You get to be a powerful and gorgeous demoness while I get to take a look at the world I haven't seen for a few hundred years or so. Plus, believe it or not, but I am actually a noble, so I possibly could still have a bit of connections alive in the noble society too."
"Don't demons kill people though?"
"Yeah, and you humans kill people too. Look kid, it isn't like I hate humans or anything, so just relax and let's just get on with this."
With that said, Nyx raises her hand and you feel yourself get sucked out of your body and pulled into her's. You now are seeing out of her eyes, and can feel her body as if it is your own. The dress, the horns, the large breasts... all of it. You have become Nyx. Your old body then disintegrates into dust as it is now little more than a souless husk.
"You will be taking a back seat for a little bit more, but then I promise to hand this all over to you" says Nyx from inside of your mind. You lose control of the body and become simply a passenger inside it as Nyx assumes control. She completes the magic and walks over to where your body once was. The blinding light returns and then dissipates as time resumes moving forwards again.