"Magic is magic. Magic is everything."
Will turned the words over and over in his mind, searching through everything he knew.
Professor Flitwick waited a moment before continuing. "Magic is, at its core, the power to change anything. Because of that, Wizards don't need to worry about their Magic when disguising themselves. If they disguise their bodies well enough, the job is essentially done. Take Polyjuice Potion, for example."
In the magical world, there were plenty of ways to impersonate someone else. The best-known was Polyjuice Potion, though it changed a person's appearance from the inside out. It could even change their sex.
"And the Thief's Downfall at the Ministry of Magic and Gringotts was designed around this property of Magic. It washes away magical influences on a Wizard other than their own Magic—Polyjuice Potion, the Imperius Curse, even Felix Felicis someone drank only a short while before."
Professor Flitwick's explanation clarified Will's understanding of Magic. No wonder the diary couldn't tell who he was.
It also brought something strange to mind. As far as Will remembered, no Wizard had ever been unable to cast spells because they had used up too much Magic. When Harry trained intensively for the Goblet of Fire, it was his aching arm that got mentioned.
Wizards who cast too much magic generally felt mentally exhausted. They might even pass out from it.
It was like playing a mage with no mana bar.
Could that be connected to the nature of Magic?
Will asked Professor Flitwick, but the answer disappointed him.
"I'm afraid I can't answer that, Will. I don't know either. Wizards have wondered about it throughout history, but very few have studied it. More troublingly, no one has ever truly solved the mystery.
"All I can tell you is that overusing Magic can