Dumbledore felt genuine shame.
Despite everything, he had not only failed to gently steer Harry toward the path he believed was necessary, he had been exposed and openly berated for his low actions. He didn't blame Julian for it. The boy had every right to be furious.
The Mirror of Erised had driven even strong-willed people to madness. Knowingly exposing a child to it was unconscionable.
Yet in his hope of ensuring Harry would never walk the same road as Voldemort, Dumbledore had done exactly that.
...
Harry and Voldemort were tied together by prophecy, and Dumbledore wanted Harry to end his former pupil's influence on the world permanently, rather than replace him as the next Dark Lord.
With Gellert free and preparing for who knew what, preventing yet another Dark Lord from rising mattered more than ever.
There isn't only bad news, Dumbledore thought with a small, tired smile. It's clear both boys are good at heart, even if one of them is misguided.
The hope in that thought was thin, but it was there.
...
Julian was finally alone with Harry, and only then did he allow himself to look at the mirror.
The sight inside it caught him immediately.
He saw an older version of himself sitting in a soft chair inside a vast library, smiling as he played with a miniature galaxy. A woman he couldn't quite make out sat in his lap, leaning against his chest, looking up at him with open adoration.
Julian tore his gaze away with effort, like ripping his hands free of something that wanted to hold him.
"What did you see?" Harry asked, curiosity sharp, clearly wanting to know what Julian's deepest desire looked like.
"I saw the future," Julian said simply, cryptic on purpose.
Then he had Harry pull the cloak over them both, and they returned to the Gryffindor dorms without another word.
...
The next morning, neither Harry nor Julian told anyone about what had happened the night before. It wouldn't help, and it would only create noise.
Instead of making a public fuss that would go nowhere, Julian went straight to the one person in the school who might actually cause Dumbledore trouble over it.
Snape.
Julian knew exactly what Lily meant to the man, and even if he never showed it, Harry mattered because of her. Julian also knew Snape would not take kindly to learning that Dumbledore had exposed Harry to something like that.
...
Julian wasn't disappointed.
The moment Snape heard what had happened, his expression turned ugly, and he vanished from Julian's sight almost immediately.
It didn't take a genius to guess where he was going.
Snape was going to give Dumbledore a piece of his mind.
It wouldn't break Dumbledore's hold over him, but it would make Snape far more cautious about leaving Dumbledore alone with Harry. That mattered, because Snape was Dumbledore's preferred tool for dirty work and for keeping an eye on Voldemort's movements, in the castle and beyond.
...
Both older wizards realized Julian was deliberately pitting them against each other.
Neither of them truly minded.
Julian had used the perfect leverage point. Dumbledore had promised Snape that Harry would be safe, and then he'd directly broken that promise. Julian's role had been nothing more than forcing the truth into the open.
If anything, both men were quietly relieved by Julian's method of venting. A talented young wizard with a lot of anger and nowhere to put it was a dangerous thing. Better that Julian burned it off through calculated moves like this, rather than turning to the dark arts.
...
There was, however, another piece of information that reached Dumbledore.
A member of the faculty, Professor Sinistra, had witnessed Julian flying the previous night.
Apparently she had been studying the heavens, as she often did, using her personal setup outside the castle, and she'd spotted him.
To be fair, Julian hadn't been subtle. His aerial maneuvers created enough air pressure and noise to be noticed outdoors, even if it wouldn't carry through the thick walls and windows of the castle.
According to Sinistra, watching Julian fly gave the impression of inhuman control over both body and broom. Every movement was precise, naturally graceful, performed at frankly frightening speed.
...
Dumbledore noted the information but did nothing with it.
The agreement between him and Julian still stood, even after the previous night.
So Dumbledore set the thought aside and returned to his real priority.
Finding Grindelwald.
Stopping whatever he was planning.
And learning why, after fifty years, Gellert had broken whatever last scraps of restraint Dumbledore had hoped still existed.