[Name] = I haven’t settled on a name yet, so just go with it :)
“Where am I? What am I doing here?” [Name] said immediately, sitting up. She was in a blank white room; neither large nor small, neither textured nor smooth, simply there, simply a place in which to be.
“You are here, in this room. Is more information really necessary?” said a man's voice, smiling. “As for what you are doing here, it is simple. You are here for the opportunity of a lifetime. Within these walls, you can do anything.”
“Anything? So I could just…” the girl snapped her fingers, looking around for the source, but there was no one to be seen, “escape if I wanted to?”
“Of course. But once you leave, you can never return. So choose wisely...”
[Name] heard none of this; after the words of course, she had closed her eyes, and by the time he had finished speaking, she had already disappeared. A man watched the scene from above, scanning the air where she had been, awaiting the inevitable. Sure enough, after a moment, a shimmer appeared in the air: the girl trying to teleport back. Of course, she did not have any sort of teleportation power of her own, but the room did have magic. After a moment, however, the shimmer disappeared, and the man sighed.
“I tried to warn you, child,” he said sadly as he drifted back to the ground. “I did say never. Shame; you could have done great things. Ah well… who’s next?”
His wings vanished as paper full of names and a pen materialized in the front of him. He caught the objects out of the air and crossed out “[Name]” with the pen. Then, seeing the next name, his eyes widened.
“Well,” he said, still staring at the name, “this should be very... interesting.”
My plan is, the next kid does the same, but for some reason the man (who knows them, haven't decided how yet) teleports them back later. "The child stood up in wonder, looking around, but there was still no one in sight. 'I thought you said never.' A man with wings floated down from far above, and when he landed gently on the floor, his wings vanished. He smiled. 'You made your decision rather hastily...I thought you deserved a second chance.'"
So in general, this man has been living here for...a very long time. If there is no one in the room, all of its magic will vanish forever...so he's been teleporting children there to see if they would be interested in this sort of power...so he can leave. All the children, however, choose home over power...until one child is given a second chance, because the man knows who she is and what she can do. When she accepts to stay, she knows that if she leaves the magic will be lost. Still, the man is watching her (she don't know this until later), and it is a battle between power and home. Thankfully, a lot can be done with this sort of power...as long as the girl is clever enough to exploit it. :D
I have a lot of other ideas, it gets DEEP with the magical logic and such, that is only part one/book one/etc ;)
(And no, the man is NOT THE FATHER so don't even suggest that XD)