Of course, Merlin was there when Hogwarts was founded. He felt the magic being drawn from the earth to create it. A cursory inspection showed nothing sinister – in fact, it was about time someone thought to make a school for magic – so he left them alone for a few years. Eventually, he decided to see what all the fuss was about so he turned up at the school one day (the gates were well warded, but their magic recognised his and they let him in) and demanded to be enrolled as a seventh year student. He emhad/em wanted to be anonymous but what with the gates, and all the wards really, just letting him go wherever he wanted, when Godric Gryffindor, sword at Merlin's throat, demanded who he was and Rowena Ravenclaw said simply, "Isn't it obvious, Godric? He's Merlin," Merlin had just nodded. "Yep. That would be me.
After that they agreed to enrol him – "Although why the hell the most powerful sorcerer ever to walk the earth would want to go to school with a bunch of incompetent children, is beyond me." "I never got taught anything, Salazar. And, frankly, I'm bored." – and plonked the talking hat on Merlin's head. Being sorted into Slytherin was not a surprise to him, Merlin had spent his first lifetime constantly sneaking around and hiding after all, but the school founders all seemed rather shocked. Even Salazar, who stared at the hat for a good minute before triumphantly crowing in Godric's face. Godric scowled, Rowena also looked rather disgruntled, but Helga simply smiled and said, "Well, since Salazar's showing off, I'll show you the way to the common rooms and get you settled in.
For a year, Merlin went to school, learnt much and taught much in return. It was the first time he had associated properly with new magic users since Camelot had fallen several hundred years ago and Merlin was intrigued by some of the changes. No one seemed to ooze magic anymore the way Morgana, Morgause, Cornelius Sigan, even Mordred, had. Eyes no longer glowed with the power running through the body and many of the spells were being said in Latin rather than the tongue of the old religion. It took some getting used to.
A couple of hundred years later, when Merlin again turned up unannounced at Hogwarts to terrify the headmaster by getting past his wards, he accepted a place working as a librarian. By now, almost all the students and staff were using wands to channel their magic and all spells were in Latin. Merlin thought they sounded dull and lifeless compared to the musicality of the old English he used. He tried to teach the staff some old magic, but they were strangely resistant. He found more fertile ground among the students, especially the first years who would all crowd into the library on rainy Sunday afternoons to hear his tales of King Arthur and the Knights of the Round Table. If he taught them some old magic while he was at it, well, who could fault him. One student, Thomas Mallory, seemed especially drawn to Merlin and his stories. Merlin was not at all surprised, some years later to come across a book of tales all about Arthur, his knights, and Merlin, the sorcerer with Mallory's name attached. Mallory had clearly let his imagination embellish the already exaggerated tales Merlin had told the young students and Merlin spent an enjoyable afternoon trying to imagine all his friends in the improbably situations Mallory had imagined them in.
"The magic was draining from the world. Merlin could feel it, gathering in little pockets around Avalon, the Isle of the Blessed, and other sacred sites of the old religion. Merlin spent several centuries in the non-magical world, watching as they created a magic of their own. They sailed around the world bringing back treasures, they invented ways to print books and images, time pieces, artwork, giant factories that could make a skein of cloth almost as quickly as Merlin's magic could. It was fascinating and Merlin spent many years at universities around Europe, learning all he could. But, eventually, the lack of magic began to pull on him. It was like homesickness. He had been away too long. Back in Albion – England – Merlin was intrigued to find out that one of those gathering places of magic was Hogwarts. So, he headed back to the old castle.
"This time, Merlin stood outside the open gates until someone came to fetch him. When asked what his name was, he told them he was called Percival Frey.
"But why are you here?" the headmistress asked.
"He shrugged, "Do you have any vacancies?"
As it turned out, they had recently created a program called Muggle Studies – "Muggle?" "Non-magic folk, you know." – but no one seemed very enthusiastic to teach it, nor the students particularly keen to take it. There were increasing numbers of "muggle-born" students apparently, which Merlin thought was probably magic's way of trying to even out the odds, so it was deemed appropriate that if the two societies were to mix more, then wizards should learn something of "muggle" life. The "pure-bloods" (and didn't Merlin scoff at that term) didn't like the idea of sullying their world with "mudblood". Merlin took the job (he had six students, all muggleborn, that first year) and made sure to make himself the most interesting and sought-after teacher in the school. Wandless magic went a long way, as did his general air of friendliness. The next year he had almost fifty students and he began to work on them. He brought muggle inventions and tasked the students to work out how to use them, he gave them muggle literature (including Mallory's book which had somehow become separated from the wizarding world), he showed them magnificent cathedrals and universities that he had travelled to, he told them about his friends the knights-who-were-not-noble and yet were the noblest of them all. He also made friends with a young Poltergeist, named it Jeeves, and encouraged it to play practical jokes on and with the students. He learned to play Quidditch and challenged his classes to matches against himself and several empty brooms (Merlin was very good at enchanting brooms thanks to Arthur). By his third year of teaching, almost every student wanted to take his class. "It's a miracle!" the headmistress exclaimed. Merlin shook his head, "No, they just want to have fun."
Merlin taught muggle studies for almost twelve years. One day, the new group of third years walked into his classroom and Merlin felt it. Magic. Not his, not Hogwarts. Magic rolling off another human being in a way it hadn't for centuries. He lifted his eyes to meet the excited, bright blue eyes of young Mr Dumbledore. The other teachers had commented on this boy's brilliance and Merlin had been excited to teach him. Apparently, he had underestimated the boy. At the end of the first lesson, Merlin said calmly, "Mr Dumbledore, please stay behind, I wish to speak to you.
The child grinned at his friends and waited obediently for the classroom to empty before turning to Merlin. Merlin began to question the boy, subtly trying to work out why him, why now. Nothing that he heard gave him any answers and he sent the boy on his way. At the end of that year, Merlin left Hogwarts once again. Magic was clearly waking up, preparing for something and so, Merlin too, needed to prepare. Arthur… Merlin refused to let himself hope, so he kept himself busy. Avalon was peaceful as ever, as was every other pool of magic. Except Hogwarts, where Albus Dumbledore was growing up.
When the muggles entered into the Great War, Merlin thought he had found his answer. He rushed to Avalon expecting Arthur to emerge from the waters of the lake, but he never did. So, Merlin joined up, once again using his powers secretly to keep his comrades alive. Still, too many died and for almost twenty years Merlin hid himself on the Isle of the Blessed.
Then, Grindlewald emerged, feeding off the latent fear and hatred of muggles that Merlin had tried to suppress at Hogwarts all those years ago. He should have tried harder. With Grindlewald came the second muggle war. Arthur still didn't return, though Merlin was sure the world would end. Eventually, Albus Dumbledore, in a duel that would go down in history, defeated Grindelwald. Merlin couldn't help being disappointed that Dumbledore's brilliance had not, in the end, been a sign of re-awakening, just of magic's need for a warrior. Still, Merlin followed Dumbledore's career carefully, watched as he refused the position of Minister of Magic and took up a role as Hogwarts' headmaster. It was almost time, Merlin decided as he once again stared out to Avalon, to return to Hogwarts.
If Dumbledore recognised him, he didn't say anything, just "Excellent, I've been needing a new defence against the dark arts teacher. You'll do brilliantly. I can only offer you the post for one year though, I'm afraid."
As soon as he signed the contract, Merlin understood why. The position was cursed. Deciding to head off a likely unpleasant scene, Merlin tendered his resignation immediately, effective at the end of the school year. Dumbledore smiled, his blue eyes twinkling at Merlin, "Welcome to the staff."
Professor Leon really preferred teaching Muggle Studies, or perhaps it was simply that the students now-a-days seemed to have divided along house lines more permanently, more resolutely, more viciously, than they ever had before and as a result it made teaching impossible. There were a group of fourth year boys, in particular, who reminded him strongly of Arthur when they had first met. Loud, arrogant, brash. They were bullies with hearts of gold. Unfortunately for them, like everything here, they picked their victims for house allegiance and they hated the Slytherins. Merlin, however, had never forgotten that he had once been a proud Slytherin, nor could he help but see himself in their victim: a relatively friendless, outcast, powerful, but hiding. Severus Snape did not have Merlin's natural charm, though, and rather than make friends as he and Arthur had done, the rivalry became more and more vicious. Merlin spoke to Dumbledore about it, scared, if not for the boy's life, then for his soul. "If he doesn't find acceptance with right people, he will find acceptance where we would not wish it!" Perhaps, Merlin reflected, he saw more of Morgana than himself in the boy. Fear, anger, hatred, power, love.
Merlin tried hard that year to temper "The Marauders" bullying. He assigned them projects that they could get their teeth into, all with an air of secrecy as though he wasn't supposed to be doing it. He even ordered Peeves not to help them with their "pranks" anymore. When that didn't work, he gave them detentions cleaning out leech tanks and scrubbing cauldrons (thank you Gaius). With their Slytherin victims, Merlin tried to be accepting and encouraging. He wore Slytherin colours although this prompted Severus Snape to say after class one day, "When were you at Hogwarts, Professor Leon? Only, you can't be that old, but I've searched through all the year books of the last fifty years and you're not there."
Merlin had chuckled, "I'm older than I look, Mr Snape."
Severus eyed him up and down and Merlin had the idea that the boy would not stop until he had figured out the mystery that was Professor Leon.
"No way were you a slimy snake!" Sirius Black exclaimed another time. Merlin gave him detention writing up a long list of powerful, influential and, most importantly, good, Slytherin alumni. Followed the next inevitable detention by a list of all Gryffindor alumni who had ended up in Azkaban and their crimes.
"Ugh, wanna swap Pads?" James Potter demanded from the other side of the room with his hands in the leech tank. Merlin's eyes flashed and the tank was suddenly three times as slimy.
"Hey!" James cried.
"Problem, Mr Potter?"
Sirius snickered.
At the end of the year, Merlin knew he had not done enough. Sure enough, barely five years later, James Potter and his young wife, Lily, were dead, Sirius Black was in Azkaban for murder and Severus Snape was on trial for being a death eater. Merlin turned up in Dumbledore's office the day before Severus' trial simply to say, "I told you so. Fix what you can." Dumbledore turned up at Snape's trial with evidence that he had been a spy. He may have been going to do it anyway. Merlin did not ask.
When James Potter's son started Hogwarts, Merlin moved to Hogsmead. He didn't trust Dumbledore with his students' wellbeing and wanted to be on hand to threaten, or intervene, should something go awry.
Harry Potter appeared to be almost as much trouble as his father, from the tales being bandied about Hogsmead. "Defeated a troll by himself." "Almost died playing Quidditch." "Killed a teacher."
"What?!" Merlin demanded when he overheard the last one.
"Yeah, Defence guy. With a turban. Apparently, he was some sort of You-Know-Who zombie and Harry Potter killed him."
Dumbledore didn't seem in the least surprised when Merlin turned up in his office that evening demanding an explanation.
Harry Potter's second year at Hogwarts ended similarly. "Oh yes, certainly, he killed a basilisk. Salazar Slytherin had hidden it away, you see, and it appears an apparition of Tom Riddle got control of it."
"Glycinda is- was still alive?" Merlin mused aloud, before realising he had bigger issues with what Dumbledore had just told him. "You mean you allowed a twelve-year-old to fight a basilisk and a dangerous apparition? Alone?!"
Dumbledore smiled again, "Not so much allowed. He certainly didn't ask permission. But he did rather well, don't you think?"
Frustrated, Merlin left in a whirlwind that he hoped had disrupted Dumbledore's office more than a little.
When Sirius Black escaped from Azkaban, Merlin acted quickly, tracking him down to a park in Surrey. There was no one there but a large shaggy dog. Merlin closed his eyes and focused. No. The dog was Sirius Black. Of course.
"Mr Black," he called, "there's no point hanging around here. Come with me, I'll get you some food."
The dog looked at him quizzically before turning jerkily back into a man. Or, at least, something resembling a man. Merlin inspected him critically. "And a bath."
Over the course of several meals, Merlin listened. Peter Pettigrew, of course. "What do you plan to do now?" he asked.
Sirius growled, "Kill the rat."
Merlin rolled his eyes, "The rat is in Hogwarts, everyone is looking for you. Let me deal with it."
Black narrowed his eyes, "And why should I trust you? I haven't forgotten that you're a Slytherin. Haven't aged a day either. Only dark magic can do that. What are you up to? Tell me! Tell ME! WHAT DO YOU WANT, YOU FILTHY SN-"
Merlin had had enough and knocked out the other man. He should have known no one would leave Azkaban as sane as Sirius had at first appeared. He settled his guest in a bed and went to Dumbledore. The office was empty when he arrived so Merlin settled in Dumbledore's chair, feet on the desk and began fiddling with the odd assortment of knickknacks Dumbledore kept. Several of the headmaster and mistress portraits woke up to speak with him and he was having a lovely conversation with Dilys Derwent when the door opened and Dumbledore walked in followed by another man.
"-him safe. It's unfortunate – Hello, Merlin – but the ministry are being particularly obstinate about this."
The other man was glaring at Merlin who jumped up and went immediately to shake his hand, "Hello, Severus, it's good to see you again!"
Severus Snape allowed the handshake before drawing away and sneering, "Well, that answers some questions." His eyes were intrigued, and slightly awestruck though, so Merlin didn't take offense and simply laughed.
"I'd wondered if you'd worked it out! Now," he turned to Dumbledore, "I should be able to solve your little problem. Sirius Black is asleep in my guest room at the moment."
Snape looked ready to fly out the room and grab the fugitive, but Dumbledore lay a gentle hand on his employee's arm. "Oh? And why do you have a criminal hidden away?"
"Oh, habit really!" Merlin grinned, then, "Because he's not really a criminal. Peter Pettigrew was the Potters' secret keeper. Sirius simply wants revenge. Apparently, a red headed friend of Harry Potter has a pet rat that's missing a finger?"
"Weasley," Snape said.
"Ah yes, Ronald. Well, I may just have to pay Molly and Arthur a visit before term starts. Make sure they're all prepared after their holiday. Severus, Merlin, would you like to join me?"
Merlin declined, but Snape agreed. Merlin almost felt sorry Pettigrew.
A week later, Merlin entered the room where Sirius Black was currently imprisoned (after the fourth escape attempt Merlin had put up magical barriers) waving a piece of paper. "I have your official pardon."
Sirius launched himself at Merlin and attempted to snatch the paper from his hand, "Nuh uh. We ask nicely in this house." It was too much fun to tease, almost like having Arthur back. Merlin pulled himself together and handed Sirius his pardon when a hand was held out for it. Sirius' shoulders relaxed as he read it and Merlin turned to leave as tears began to fall. "You have visitors coming in half an hour. Make sure you have a shower."
The reunion of Sirius Black and Remus Lupin was as joyful as the reunion of Sirius Black and Albus Dumbledore was awkward. Merlin didn't enjoy such scenes, so he left them to it, returning to find Dumbledore had left the two old friends together after offering Remus the job of Defence teacher.
"It's cursed, you know," Merlin warned.
Remus didn't seem put off and Merlin was pleased to realise, by the end of July, that for once, Harry Potter had not had his life endangered at school. Merlin still ended up in Dumbledore's office, though.
"Remus obviously can't come back and Sirius is still… he still needs some more help before he can teach." It was the understatement of the century, but Merlin couldn't turn down the opportunity to get closer to Harry Potter than before so, once again, Professor Leon was the Defence against the dark arts teacher.
The first thing Merlin noticed about Harry Potter was how much he looked like James Potter. The second thing he noticed was how much Harry Potter didn't act like James Potter and the third thing he noticed was that a cloud of very, very dark magic hung ominously around the boy. Experience had taught him not to bother going to Dumbledore, so he just asked Harry to stay behind after class.
"Does your scar bother you?"
"I get headaches sometimes," the boy admitted, rubbing at the scar.
"Hmm. I used to be a phy- doctor. Let me have a look."
The boy was too trusting for his own good, but Merlin wasn't out to hurt him. Merlin took the boy's face between his hands and send a tendril of magic into the scar. It was definitely the source of the darkness. He probed some more as the magic fought back as though it had a mind of its own. Merlin thought he could destroy the whatever-it-was but it would take a lot of magic. "Are you ok?" Harry looked a little pale but nodded. "Right, this might hurt, but you've got some sort of infection in that scar and I'm going to get it out. Ok?" The boy just gritted his teeth so Merlin started again. He flooded magic into the scar, drawing the purest magic he could from himself, Hogwarts and the earth. Finally, he felt something give way. Harry cried out and reached to touch the scar but Merlin needed a little longer so held his hand away. Tears were leaking from the boy's eyes and black blood was oozing from the scar when Merlin finally felt all the traces of dark magic burnt away.
He wiped the scar with a tissue and cleaned it up as best he could, sucking all the infected blood out before sealing it with a quick healing spell. The scar closed, pale and white and almost invisible. "I'm very sorry about that Harry, but I've removed the infection," he showed Harry the black stained tissue, "and your scar shouldn't bother you now. Come on, we'll go and see Madame Pomfrey. She should have something for your headache."
Merlin was not surprised when, this time, Dumbledore appeared in Merlin's office. "What did you do?"
Dumbledore sounded angry, as though Merlin had messed with his favourite toy. He probably had. Enough was enough. Dumbledore had been the top dog in his own little world for so long he'd forgotten that no one (except maybe poor Severus Snape) was actually obliged to tell the headmaster anything. Merlin let his power leak out and infuse his voice when he said, "I did what you should have done long ago." To make the point a bit more, Merlin wrested control of Hogwarts out of Dumbledore's grasp and let his power and Hogwarts' power infuse the little room so that, had he actually been human, breathing would have become difficult. Then he let it all go. Hogwarts returned, slightly unwillingly, to the control of the headmaster. When Merlin next spoke, his voice was normal, cheerful, as though he hadn't just deliberately almost frightened Albus Dumbledore to death. "I don't answer to you, Dumbledore."
Harry Potter seemed much more cheerful the rest of the school year. He joined in enthusiastically as the rest of the school cheered for Cedric Diggory, he infuriated Severus during potions lessons – "He's just like his father! Arrogant! Stuck up! Bullying!" "Is he, though, Severus?" – and he even had his own little teenage angst moment at the Yule Ball where Merlin was amused to note both Harry and Ron Weasley ignored their dates to sulk instead. Cedric Diggory won the tournament and Merlin announced his retirement. Later that evening, he and Remus re-introduced Harry to Sirius Black who had just been released from St Mungo's with a clean bill of health. Merlin thought he needed more watching, but he was certainly sane enough to become Harry's guardian.
Fifth year, was, luckily, uneventful again. Sirius and Remus job shared the Defence post. Merlin made another trip to Dumbledore's office. This time he took control of Hogwarts without the display of power and simply refused to give it back until Dumbledore told him everything. Which was how Merlin found himself Horcrux hunting. Having destroyed the one in Harry Potter's forehead, Merlin found it relatively easy to locate the others, they were like dark blots in the tapestry of the earth's magic. One was in Hogwarts. He destroyed that one first, mentally apologising to Rowena for what had become of her beautiful diadem. Dumbledore accompanied him to a shack in the middle of nowhere and almost got himself cursed. Merlin thought that maybe he should have just let it happen. This time, he showed Dumbledore how to destroy them. Turns out, Dumbledore was powerful, but his magic wasn't light enough to burn up the horcrux. He used basilisk venom instead. Merlin couldn't help but wander exactly what Dumbledore had been doing with his long life. The locket (which earned Merlin a house elf much to Sirius Black's joy) and the cup were easy enough to get rid of.
The last two, Merlin sensed were more dangerous. One was a snake, the other a wraith. Of course, the others had fought back, throwing out disturbing images of Arthur or Gwen or Morgana or a young girl pleading for her life when Dumbledore approached. But these would be different, and Merlin was tired. So, he headed out to Avalon for the summer. He spoke to the lake, to Arthur and Freya and Lancelot. Even to Morgana who he had buried there, too. The only reply was the soft whooshing of the water against the bank.
At the beginning of September, Merlin, Dumbledore, Severus Snape and Minerva McGonagall (who Merlin had had a strategic conversation with about not letting Dumbledore dictate everything) set off to battle the last two horcruxes. They were together – "The old Riddle House," Dumbledore said, knowingly when Merlin showed him where on the map – and protected by only one other person.
In the end, it was all rather anti-climactic. Minerva dispatched the snake with a little help from Godric Gryffindor's sword; Dumbledore subdued the painfully thin, wild eyed man standing protectively in front of a bundle of rags. Severus stepped up to the rags and pulled them away. Merlin couldn't see from where he stood in the shadows, ready to fight but willing to leave this to those whose fight it was, but Severus' face showed disgust and hatred and pity. "Ssseverusss. Are you here assss traitor or-"
"Avada Kedavra."
Merlin finally approached and reached out with his magic, but there was no need. All traces of horcrux were gone. "He's gone."
Merlin left them there, a huddle of emotions and friendship and loyalty he wouldn't be part of again until… He went to Harry Potter instead, popping up in the Gryffindor common room and startling a group of second years whose game of exploding snap he ended up in the middle of. "Harry."
Obediently, Harry Potter tripped across the common room to where Merlin beckoned. Still to trusting for his own good, but that mattered little now. For the first time, though, Merlin sensed the boy's power, rolling off him as Dumbledore's had done many years ago. "Harry, this is not public knowledge, but I thought you should know. Tom Riddle is gone. Forever."
"But I thought-"
"Yes, so did a lot of people. I have learnt that destiny is what we make it. Never let yourself be a slave to it, Harry. Just live your life."
"Oh. Okay."
"Now, listen to me. You may see me again, you may not, but you have been given a gift, Harry. Use it wisely. You are powerful. Extremely so, but that is not what I'm talking about. You are hopeful and kind and loving. Not all of us are or can be those things. Do not get lost in the power but hold onto who you are."
Harry's green eyes were wide, and Merlin had the sinking suspicion that the advice he had just given the boy had sounded a lot like some twaddle that Dumbledore would spout. Or, worse, Kilgarrah. So, he added, "And give us Slytherins a chance, hey? There are different ways of being a hero and not all of them involve flashy swords and fights. Some of us work best in the shadows. It doesn't mean we do any less. Oh, and try not to antagonise Professor Snape, I need him not to quit to keep the headmaster in line!"
Harry grinned at that, "I'll try, sir."
"And, just so you know, you act nothing like your father. It's your mother that I see in you, and I suspect Professor Snape could too." Merlin rather thought he'd said more than Severus would thank him for on that subject, so he ignored Harry's startled, "What?!" and said simply, "Don't you have some homework to be getting on with?"
"Professor Snape gave us a whole two feet to write on inferi," Harry grumbled. "And Professor Flitwick gave us three feet on expansion charms."
Hermione Granger interrupted then, somehow sensing that the confidential part of their chat was over. "Professor Leon, how did you apparate here? Only I read Hogwarts: A History and it says apparition is impossible in Hogwarts."
"I can do a lot of things that most people think are impossible," Merlin said simply, before apparating back out.
He landed on the shores of Avalon. Again. "I really thought this time would be it," he told the air, "but in the end, it wasn't much of anything."
A car whizzed past on the road in the distance and Merlin wandered fatalistically how much longer he'd be able to protect the last well-springs of magic. "Come back soon, Arthur. Please."
Twenty years later, Merlin was somehow not surprised when the young man sitting on the shores of Avalon, happily chatting to a bewildered Arthur turned out to be Albus Severus Potter. "Potter," he sighed, "what have you done?"