Warning: This story includes minor spoilers from Fantastic Beasts 2: The Crimes of Grindelwald. Please watch the movie first or read it at your own risk.

The main pairing is Grindeldore (Albus Dumbledore/Gellert Grindelwald). Again, don't read this if you think you could have a problem with that.

It would have been a shocking sight for anyone else. One of the most powerful dark wizards of all times, standing in front of an innocent, helpless child.

The old wizard's face, severely emaciated and worn by time, still showed a glimpse of his ancient strength when his mouth curved in a mischievous, threatening smirk. His white right eye glimmered in the shadow as his cheek wrinkled up, adding to his menacing appearance. Yet the young boy didn't seem intimidated. He sat on the cold floor with his legs folded beneath him, looking up at where the wizard stood with dreamy, tearful eyes as if he were contemplating a beautiful but gloomy painting.

In fact the old wizard's smirk wasn't directed at the boy. He hadn't notice the child at all. His gaze was pointed past his head to the dark room behind him. His attention was all focused on the other old wizard who had just entered the room without making a sound. Albus Dumbledore. His smirk was for him.

Dumbledore was looking back at the old wizard. He knew he would have seen him even before stepping inside the room. He was always there waiting for him. Almost always. But even when he wasn't there, the though of him, Gellert Grindelwald, seldom left his mind.

If anyone else had entered the room in that moment, they could have witnessed one of the most bizarre scenes of their entire life. A little boy of enormous fame, Harry Potter, sitting in the same room as the two most powerful wizards the Wizarding World had known in centuries, but completely oblivious of them. That was because Dumbledore was making every effort not to break the silence of the night. Because Harry was too captivated on the memory of his lost family. And because Grindelwald wasn't actually there.

He was locked inside a mirror, as a reflection. Not any mirror, mind you, the mirror. The Mirror of Erised.

Dumbledore shifted silently, dragging his heavy robes across the floor. Grindelwald's eyes followed him until he had moved too far to reflect in the Mirror. Then Grindelwald disappeared, knowing he'd be back soon.

Dumbledore let out a sight and brushed his long beard with his hand. Seeing Grindelwald always brought back such an intense muddle of emotions. Still, he had to move closer to the Mirror again if he wanted to speak to Harry. And he had to. He couldn't let that young, brave boy spend another sleepless night in that room. He had to save him from the monstrosity that mirror was capable of turning a person into.

Harry seemed caught in a trance and hadn't blinked once since Dumbledore had entered the room. He didn't want to break eye contact with his parents, smiling and waving at him from inside the Mirror, fearing that if he closed his eyes they would disappear. That was the spell the Mirror cast on anyone who dared look at it.

"Back again, Harry?" Dumbledore finally said, moving towards the Mirror. Grindelwald's image reappeared, his grin widening.

Harry stood abruptly, panicking, as if his darkest secret had just been unveiled.

"I see that you, like so many before you, have discovered the delights of the Mirror of Erised," continued Dumbledore, trying to show empathy in his gravelly voice. After all, he was not only among the ones who had been hypnotized by the Mirror, he was also one of those who had spent way too long contemplating its fake promises.

Grindelwald listened intently as Dumbledore explained to Harry what the Mirror was and why it must be hidden, somehow amused by the conversation. Dumbledore tried not to look at him – Harry's safety was his main concern – but the fascination Grindelwald was able to exert on him even through a glass was too strong to resist the temptation. Their eyes met now and then, carrying a parallel, silent conversation while he was talking to Harry.

You would expect that after years – decades even – of silent conversations through a mirror, he had now got used to it. But Grindelwald still made him feel an eerie sensation on the back of his tense neck.

Sometimes, during his early days as a teacher at Hogwarts, when he still taught Defense Against the Dark Arts and moving against Grindelwald seemed impossible, he would spend hours in front of the Mirror. He had let the Mirror get inside his head in a way no sane person should ever allow themselves to do. When he though no one could hear him, he would question Grindelwald, ask him why he had to take that path, why everything had to go terribly wrong. And after a long cry, sometimes he would caress the Mirror, recalling his younger years as a nostalgic old man.

How many sleepless night he had spent collapsed on the floor in front of the Mirror, exactly like young Harry? When he lowered his defenses, the long lost dreams he had shared with Gellert would escape his mouth in a whisper, almost wishing he could turn back time and be there again with him.

Oh, that summer, those blessed few months when magic was more tangible than ever and making an impact on the world seemed possible – an impact that wasn't just making up for his own terrible mistakes, feeling he'll never be worth of any love or forgiveness again.

Sadly, the only impact of their relationship was on Dumbledore's life. He had found, and lost, love in Gellert – if that even was love. He was only sure it came at much too high a cost.

Crazy how a such a little period of time had changed his life for good. No one could ever guess what would have been of him if he hadn't met Gellert, or worse if he had followed him until the end, but in many days the weight of those lost possibilities was the realest thing in his life, and a mirror the closest bond he had.

"It does not do to dwell on dreams, Harry," he said, gathering the wisdom that experience had cursed upon him, "and forget to live." Sometimes your dreams can destroy your life.

Sorrowful wisdom was met with childish, lively naivety. "What do you see when you look in the mirror?" Harry asked him back.

Dumbledore was startled out of his memories by the boy's cheekiness. With the corner of his eye, he noticed Grindelwald's gaze become more intense, as if he were challenging him to answer.

Well, there wasn't a simple answer to that question, he thought. Not only because there wasn't a simple way to explain his relationship with Gellert, but because he wasn't the only person to visit him through the Mirror either. He had found out that what he saw tended to change depending on what he regretted the most, and what he was feeling most guilty for, on a particular day. But also who he missed the most.

Ariana had been the first one to appear in the Mirror, and had frequently visited him throughout his life. Once he had been able to push back the tears at her sight, he had studied her face carefully, trying to detect any expression in her eyes – anger... pity... forgiveness? What his sister had thought of him in the last moments of her life was still a mystery to him, one that would forever haunt him.

Often times she was joined in the Mirror by Aberforth and their parents, all peacefully and harmoniously together in one embrace. A bliss they'd never experienced in life, and maybe the only thing that could have prevented further misfortunes to befall them.

But the far most frequent – and most cruel – manifestation on the Mirror was Gellert. Seeing the criminal alongside his victims was ironic, yet he had never seemed out of place to Albus. If he had to attempt to define his connection with Gellert, the only fitting word would have been family.

That did not prevent him to be often ashamed of that vision, though, and wish Gellert could disappear from the Mirror to never be back.

He had tried to strengthen his mind to free it of the twisted, manipulative thoughts Gellert had clearly infested it with in order to follow him around forever, but in vain. He had only became more similar to Gellert in the process. People would now accuse him of being a great manipulator himself – and they were right. He was able to influence people's life permanently, and not always for the better. But it couldn't be any other way. If his time with Gellert had taught him anything, it was that sometimes things need a push to achieve a greater good. His only consolation was that, unlike his former friend, he had a morality. But he wasn't sure whether that was just a story he told himself to fall asleep at night.

Despite his training to cut off Gellert from his mind, nothing had changed. Maybe he was weaker than everyone thought. After all, it had only took a few weeks of flattery to fall in Gellert's trap. His hopeless need for validation had become a dangerous weapon when he was young and romance had blinded him, and that part of him could never take over him again. Having students, colleagues and half the Wizarding World rely on him had made it easier to do what was right, but learning to master sentiment had been a long and complex operation – and despite his calm, reassuring facade, his wise and rational thinking, his powerful skills, he still felt vulnerable. All the people thinking he was capable of solving every problem with a flick of his wand – what would have they thought of him, had they known he was as human as they were?

Over time, Albus had tried to convince himself his desire to go back to his teenage days was just out of regret. He regretted not being able to stop Gellert before he became a monster, making him see reason. Maybe if they could do it all again, they could do it right this time. But deep down he knew Gellert was already beyond saving when he met him.

Only when he had finally accepted that regret would never leave him, he started to understand. It didn't matter how short their relationship had been, he still carried it with him because in that moment he had allowed himself to express his untamed potential for the first time, knowing there was nothing Gellert wouldn't have accepted or understood, unlike anyone else. He had explored parts of his soul, and found things within himself, that could never be unseen. His time with Gellert had left an indelible mark on his life.

To understand why he still wanted to be reunited with him, he had to delve in the darkest, maddest part of his soul, which he had never unleashed since. What he was seeing in the Mirror was an echo of their connection, and he had to admit he had never felt a similar connection to anyone else throughout his life. Someone who was truly his equal, able to think like him, to change a person's heart with the right word, to push his mind to the extremes of human understanding.

The reality of his long, lonely life was that no one else had ever matched up to Gellert. Having that old connection back – having Gellert back to his side as he was when they first met all those years ago, without the tragedies and the cruelties he caused but the same wit and spirit – that was a dream he still hadn't manage to get rid of...

Harry was still looking up at him, waiting for an answer.

That young, clever boy, standing in front of him with inquisitive eyes, was the closest thing to a familiar bond he had had in years. He was someone to look after, take care of, and protect. As he had done for his sister, only better this time. And yet he feared he wouldn't be able to save him from darkness either.

Harry's expression urged him to answer, but how could he explain to an 11-year-old boy that he saw in the Mirror someone who once was closer than a brother to him, and now was his biggest regret? He couldn't show any of his torments to the boy. Harry was suffering with his own losses and didn't need an old man's grief on his shoulders.

None of his ready-made inspirational answers seemed appropriate in that moment. Even though he wasn't able to tell him anything that could give him hope, at least he could try to lighten his sorrow. Make him smile.

"I?" Dumbledore finally said, his weary eyebrows dropping off. Harry stared.

"I see myself holding a pair of thick, woolen socks."

A/N: This is my interpretation of Dumbledore and Grindelwald's relationship, especially Dumbledore's feelings. I first had this idea when the last Fantastic Beasts trailer come out, but I waited until the movie was released in cinemas to be sure to express Dumbledore and Grindelwald's chemistry properly. I hope I managed to capture a fraction of what Jude Law and Johnny Depp showed on screen. Amazing performances both, the highlight of the entire movie for me.

Have you watched The Crimes of Grindelwald yet? Did you like it? Tell me your opinions on the movie and my fanfic below in the comments, I would really appreciate your feedback.