A/N: Thank you to my wonderful brother for beta reading this for me.

Character Versatility Challenge - prompts: Albus Dumbledore, Gellert Grindelwald

It was the mystery that eternally hung over his head like catnip held just out of reach by a particular cruel owner. He was able to swipe at the dangling treat, but he could never quite get his paws to close around the desired answer. Every time he made a move for it, it was tantalisingly jerked around and then swiftly reeled away, leaving him feeling bereaved and off-kilter.

At first, he had been determined to solve the enigma. Blinded by a treacherous combination of extreme intelligence, youthful arrogance, and undeniable inexperience in the real world, he had taken comfort from the fact that he had never encountered a problem he hadn't eventually been able to overcome.

Surely, he had thought, suppressing the part of his brain that whispered mutinous thoughts to him, this will be the same; I will find the answer, and it will exonerate me from this guilt.

He had been so confident about it. Even in the midst of the darkest of depressed nights, hope had routinely flared within him like a phoenix rising from the ashes of disappointment and destitution. Every time his mind had supplied an answer to satiate his sense of burning shame, something else had come to mind that refuted the conclusion in question.

Every time he'd thought he had worked out which spell it had been, or who the caster had been, he had spotted another burst of magnificent light that could just as easily have been the curse that did it. All three of them had been flinging around some rather nasty curses, after all; there were a myriad of possible death-bringers to choose from.

It might have been him. It might have been Gellert. It might have been Aberforth. It might have been the tragic result of two dark, volatile forces colliding and reacting to one another with unprecedented violence.

Well, in hindsight, it most certainly had been that. To his great shame, there was no other way to describe what he and Gellert had both become in their pursuit of absolute power. They had been so eager to wield it for the good of all wizard-kind, but their eyes had adjusted to the darkness that they had studied with such dedication, and it had reached the point where Albus had no longer been able to make out the lines he'd once oh-so-nobly drawn in the sand.

At the time, however, he had done his best to suppress any semblance of real self-reflection. The horrors that tickled the back of his mind whenever he let his attention drift had already been too much to take, so he'd thrown all of his efforts into the presumably productive practice of perusing the memory to see if he could spot something new. He had revisited the memory so many times that it had begun to feel like her lifeless face was branded into his mind like a haunting tattoo, but it had numbed the pain, even for a brief while, so he had pressed on with the macabre task.

Still, his searches had been futile. No matter how hard he'd tried, he'd never been able to get past the possibility that either of them could have been the one to throw that deadly curse.

So, over the years, he had learned to ignore his thirst for an explanation. As much as he knew that true closure would never come until he had his answers, he was painstakingly aware that they could just as easily send him into a dark spiral of bottomless descent from which there would be no coming back.

Besides, he, even decades later, wasn't quite sure he even deserved closure. Maybe it was eluding him for a reason. Perhaps he had been sentenced to purgatory, bound to be endlessly tortured by the sorrow and guilt until he proved himself worthy of forgiveness or died.

Nevertheless, he yearned for it. The tireless years spent rebuilding his life and fighting back against Voldemort had taught him that some questions truly weren't answerable, but he had never before encountered an unsolvable problem of such magnitude and personal importance.

Furthermore, he owed it to her to know and honour the circumstances of her death. It was hard to fathom celebrating the life of someone who might have died at your hand, but it was surely more respectful to know than to go on in perpetual ignorance. He owed it to her.

He'd owed it to her to do a lot more. Investigating this matter was a small recompense for what he'd done, or let happen, to her, but it was the best he could do. 'The answer' had built up in his mind until it was something he was both desperate for and terrified of, but, at the end of the day, the identity of the person who had cast the killing blow didn't much matter. Either way, it had been his own folly that had created that situation in the first place, that had set the stage for the duel to rise out of. Either way, it was his fault.

So he was determined to do what he could to alleviate the never-ending pain. For him, that meant investigation – and it meant ensuring that that sort of thing never happened again. His quest for personal reprieves had landed him in multiple stations of great influence, even with him refusing to take the position of Minister for Magic, and had inadvertently given him the power to protect humankind from future dark wizards and to attempt to advocate for the oppressed.

Therefore, although it didn't do her any good, he remained strong and, in her memory, championed for the rights of Muggle-borns and Squibs, of half-breeds and the downtrodden.

And, in his spare time, he wandered to the room where he'd hidden the Mirror of Erised and stared into the pale blue eyes that stared back at him from its ornate glass surface, pining for the sister he'd lost. The image of the three siblings, silver hair framing their faces as they laughed together, captivated and entranced him as if he were a Muggle-born seeing a pretty light show emanating from a professor's wand for the first time. Knowing the risk of abusing the mirror, he had decided not to store it in his own bedchambers, but he still couldn't resist visiting it regularly just to see their happy faces smiling back at him as the legendary mirror fooled him into forgetting the horrible truth for a few fleeting hours.