Becoming the Master of Death by uniting the Deathly Hallows came with some distinct changes Harry was beginning to discover. Notably and maybe expectedly among them was immortality. There was a sort of cruel irony to obtaining such immortality without meaning to, especially in order to kill Voldemort, with his flight from death fantasies and all.
Honestly, the way that the great Harry Potter found out he was immortal was rather embarrassing.
He hit his head. It turns out that regardless of magical prowess or strength of will all humans are susceptible to lethal levels of clumsiness.
And so the infamous Boy-Who-Lived died, his corpse resting at the bottom of the stairs in his modest apartment. It had been a few years since the "final battle" and Harry had gotten his own flat, figuring Grimmauld Place wasn't ideal for his mental health. He woke the next morning as if he'd had a bad night's sleep, took a few moments to pat over his still-breathing body and freak out, and then with a sigh and familiar shake of his head he got back up and walked upstairs without a spill this time.
It was after this first death that his duties as the Master of Death began to crop up. Occasionally, maybe once a month or so, he would be transported near someone at the very end of their life. There was never anything he could do for them, Harry found, his war-tested healing spells useless in the face of their condition no matter what it was. His arrival was also jarring at first, the abrupt and unavoidable teleportation that happened seamlessly, so unlike the magical transportation methods Harry was used to. Oh, and the being with strangers on the verge of unavoidable death.
Eventually, it became routine and Harry started to understand more about his role beside these ill-fated strangers. They were always alone, in almost every sense of the world. No family, no friends, no pets. They were never rich, well-off, or in a very luxurious location. And they were always, always doomed.
As such, Harry began to do the only thing he could think to. He stayed. He stayed by their side as they passed on. Some regarded him as a harbinger, some spectral sign of the grim inevitable, and would ignore him, hoping against hope he would go or merely set against the idea of talking to a stranger in the end. Others, however, would grant him their attention and thank him, whether while gasping through grievous wounds or calmly acknowledging him with often knowing tones. He offered what comfort he could, a hand rested on weathered hand or bloodied shoulder.
He started offering cigarettes at some point too, unintentionally at first. An immortal was allowed more vices than the average wizard and once he allowed that excuse for himself it was easy to make sense of offering them to the damned as well.
He explained away his new circumstances to his friends honestly, while playing down how it affected him. Harry figured that he'd rather Ron and Hermione know than surprise them during a dinner when he suddenly disappeared, no crack of apparition to be heard. They experienced these disappearances of his a few separate times throughout their lives and when they and the others Harry cared about passed on over time, he found himself needing to explain less and less.
He began to seclude himself from the ever-changing, ever-aging world. His duties carried on, a constant, morbid presence that Harry was somewhat thankful for. He never became desensitized to them, the deaths of these strangers, but neither did he vomit as soon as he was transported away from their corpses anymore. He had his own grief and he could sit or stand with another as they came to terms with the end of their life. Smoking became his pastime and the cigarettes that he offered became higher quality as he delved further into it. He found himself well-dressed more often than not in more recent days; at some point he had determined that dark formalwear was the least he could offer those that didn't want to acknowledge his presence or turned down his go-to cigarette.
A strange group of muggles eventually began to take notice as computers and cameras and everything else seemed to grow more advanced by the day. They saw him on hospital security cameras and one fellow even photographed Harry himself before passing on minutes later. It was funny to Harry that for a second time in his too-long life he had become famous for something out of his control. The group never attempted to predict who he would be summoned to visit and seemed content to merely quell his growing urban legend as long as he continued his routine. And so he did.
Being the Master of Death became his life, unfortunately. It was never his intention of course, but his cruel mistress refused to negotiate her terms despite the title implying he had some sort of power over her. In reality, he often thought he was most likely a simple anomaly. He had ended up with items that prevented his death and she repaid his unnatural act by giving him a job to do every now and then. And so he would.
Author's Note: This is my first piece of fanfiction writing I've ever felt good enough about to post. I'd appreciate knowing if anyone enjoyed/read it through any reviews or comments you may have! It's been exciting to go through the process of finally putting something out there. Thank you!