Merlin smiled at Katie's reaction. "Yes, I am THAT Merlin, and I tend to pop up when young people are facing their greatest destiny. As it is, your finding the ring was probably not an accident, and since you wished your friend Bobby to forget its existence, that takes care of his mistake."
"Well, I mean, I didn't want to hurt him or have him come to Mom at school looking for the ring," Katie said.
"I know you didnt, dear. I forget after all you are still a little girl at heart, that's why the ring works for you. The ring only works for those who truely still believe in magic. Were you to wish yourself into a full adult, it might not. As it is though, I would like to make a proposal to you?"
"A proposal?" Katie asked.
"Yes," Merlin cleared his throat. "I sense you could have many, many more wonderful adventures with this ring as it is, however, I could also augment it. In so doing, the ring couldn't just control ages of people, i could transform them as far as your imagination wanted."
"But...?" Katie ventured, knowing there was a catch.
"Well, you can't use it to hurt anyone or do something malicious. Mischief is fine, mischief seems to inherit these rings. The catch is, the more you use it, the more magical you might become yourself. These rings were meant to be used by my own successor."
"So...I'll be a magician?" Katie asked.
"Yes, dear. The more you use it the less "real human" you might become."
Katie pondered the man's words. "I would never use it to harm someone, unless they harmed me. Is that ok?"
"Yes indeed, the ring will naturally defend you from harm or from being removed from your person, without you willing it. BY the same token, if you freely give it to someone, it can be used on you."
Katie nodded and closed her eyes. She could keep the ring as it was....or let the wizard augment it, or perhaps find something else