"They said it was a dark and stormy night when the two wizards met, thunder and wind screaming as they met in the center of a muggle city. The statues of muggles overlooked them as clouds gathered over their heads. It was almost as if the storms themselves were holding their breath, waiting for the beginning of the duel." Sirius said.
Fabrications for dramatic effect, if I were to guess.
Harry agreed.
"Then, without a word, the two raised their wands and began. Gellert attacked first, weaving threads of dark magic and cursed fire to throw at Dumbledore, whose protective charms broke against the attacks. He tried to dodge, but was consumed. The onlookers screamed then, they thought he was dead."
"What? How did he survive?" Harry asked, caught off guard.
Sirius shrugged. "I don't know, and I'm not sure anyone else did either. But when the smoke cleared Dumbledore was there, unharmed. Nobody had seen him cast a spell, he didn't even raise his wand." He said.
"What? That's stupid, how is that even possible? How reliable was this?" Harry demanded.
Sirius shrugged again. "This was one of my fellow students who claimed to have read about it from a book during a history of magic lesson. The book's author was one of the witnesses."
Who probably was more interested in a fanciful tale than facts.
"Anyhow." He continued. "Dumbledore attacked. He didn't use spells, Gridenwald had created a barrier of fire to guard himself. Instead, he used transfiguration. Air turned to water and into ice, but as they came near Grindelwald summoned a shield, but Dumbledore turned it back into air again and fire when they arrived before Gridenwald." Sirius said.
"Dumbledore can turn air into fire?" Harry asked.
Sirius put up his hands. "Please, Harry. I have no way of knowing. Now, can I finish?" Harry frowned but nodded.
Sirius' voice grew distant, his eyes clouding. "It was as if the elements themselves were his ally. Water turned into flames above Grindelwald's head, and the air rushed forward to strangle him whenever he tried to cast a spell. Dumbledore casted no spell, but his attacks were more powerful than a spell could ever be. Whenever Gridenwald's spells drew near they turned to ash, and floated away into the wind."
Ridiculous, why did he get hit the first time then?
"So many times it seemed like Dumbledore was dead, struck down by one curse or another he could not defend against in time. Yet when the smoke cleared he was still there, attacking Gridenwald. In the end, it was the smoke that defeated him, silver smoke that Dumbledore conjured from the spells Grindenwald casted. His spells were muffled, and even as the sky filled with dark spells and killing curses it had no effect. By the time Dumbledore had reached him Gridenwald had collapsed, and he was drained of strength. He opened his mouth to curse him, but it was useless. He seemed befuddled, and casted it into the air at random, screaming. He lost, and though nobody knew how Dumbledore had won the duel." Sirius finished.
"Uncle Sirius, is this story realistic?" Harry asked.
If he thinks so he is a fool.
He sighed. "As I said, Harry. The truth is probably lost somewhere in between. Ask long enough and you will find thousands of different versions, all ending the same. If you wish for the truth, perhaps you should find Dumbledore himself. He never told me, and if he did I never heard." He said.
"Dumbledore sounds strong." Harry observed.
Sirius nodded. "Most call him the strongest wizard to ever live. Not just for his power in duels, either. Some would call him the wisest, or one of the wisest at least, among those like Merlin."
"Is there anyone who could fight him? Win?" Harry asked.
Sirius' brows furrowed. "Fight? None alive that I know of. Perhaps a group of wizards and witches, but that's a different story entirely. Depends on who, I would say. If it were lesser wizards or muggles he may never lose, but against the most accomplished of our time? Perhaps a dozen, perhaps more. Few would be able to stop his flight unless they lured him into a trap, and only Merlin knows who could do such a thing." Sirius shook his head. "No need to think about such things Harry. You're talented, maybe even a match for him in the future. But not now."
"Nobody in the future? What about the past?" Harry asked, staring at his godfather with curious eyes.
"The past? Merlin would be a match for any wizard. The founders of Hogwarts were not far behind him in strength. There is Voldemort, and Gridenwald, who many would say is stronger." Sirius said with a frown.
"Gridenwald? Didn't he lose the duel?" Harry asked.
"He did, but there is more to power than duels Harry. Gridenwald has access to dark magic Dumbledore would never stoop to using, and his mastery of them makes him a fearsome opponent. Dark wizards of the same skill almost always best those of the light. Dumbledore only won because he survived attacks no wizard should have, and to this day none know how." Sirius explained.
"They're so powerful? Can you show me?" Harry asked, grabbing onto Sirius' sleeves again.
A grin crept across Sirius' face. "Well, you see...." It faded just as it came. "My mistake, I shouldn't have talked about it."
"But-" Harry started.
Sirius cut him off with a stern voice. "I will not, Harry. I made promises to your mother. Ask next time she comes if you want to so much. If you wish to learn things you should not, it will not be from me." He said.
Harry sighed, but nodded. "I'll ask when she visits." He said. He stared at the sky, wondering where his mother was now. It almost surprised him to realize that he already missed her. When would she visit? Hopefully soon.