Disclaimer: Marvel and HP don't not never belong to me.

Beta read by the awesome Nyx the Author. Thanks!

A/N: There was a reader question about the mirror dimension. Specifically, that sorcerers can only fold space in the mirror dimension when they have access to the power of the Dark Dimension, hence why Kaecilius made the deal with Dormammu in "Dr. Strange".
I watched the relevant scenes again just to double check, and the Dark Dimension certainly gives sorcerers more control in the mirror dimension, BUT I don't think that's the only way to do it.

In the scene where The Ancient One first introduces the subject to Stephen Strange, she is explaining how it works and then folds space in front of him. Why do that, only to later say, "You know that power I showed you? You'll never be able to do it." She later only expresses shock that Kaecilius can fold space OUTSIDE of the mirror dimension, implying that any sorcerer can do it inside. The power of the Dark Dimension allows you greater power in the mirror dimension, AND the ability to fold space in the normal world.

If a future Dr. Strange film contradicts this explanation, oh well. This is the reasoning I'm going with for this story, and Kaecilius gives some exposition on the subject in this chapter.

More A/N at the end. Enjoy!

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Chapter 13: Learning and Letters

July 1

"Focus, Harry. You are in control now. Don't let me grab it back from you. Keep everything motionless."

Harry had both hands splayed on the floor of his bedroom, eyes closed and teeth gritted. Kaecilius had been working him to the bone for the past week, intent on teaching him the basics of how to control the mirror dimension. While he had only been able to take the control away from his teacher for seconds at first, the intervals had steadily increased. Today, for the first time, Harry had a firm hold on the dimensional space and refused to let Kaecilius take over again. Sweat was pouring down his face from the effort, but he would not give up.

After keeping the room unchanged for over a minute, Kaecilius smiled and said, "Well done. Release it."

Harry collapsed bonelessly to the floor and for the first time, it didn't move beneath him. Kaecilius let him lay there for a moment, then helped his apprentice to a chair. After Harry had caught his breath, the man said, "I have good news and bad news. The good news is that you are now ready to begin manipulating the mirror world yourself, folding matter by your own will. You're also ready to work on other magic while you're here."

Harry smiled widely, relieved to finally start moving forward. "And what's the bad n-news?" he asked.

Kaecilius looked rather smug as he replied, "For the past week, I have been putting in the bare minimum of my concentration on manipulating the mirror dimension against you. Now that you've proven you can handle that much, I shall be making a real effort."

Harry groaned. "Thanks for the ego boost."

His master waved off Harry's complaint. "Don't mistake that as an insult. You are quite young, pitting yourself against an opponent with years of experience. The progress you've made is considerable. I just want you to be prepared in case the worst happens."

Harry looked up with confusion. "Like what?"

His teacher looked uncomfortable, as if unsure he should be sharing this much. "Well… what you must understand is that the mirror dimension isn't… empty. Sorcerers have been using it for millennia as a place to train, to hide, and to spy when necessary. But it can also be used to… contain threats."

Harry felt the hair on the back of his neck rise. "Threats? L-Like evil sorcerers?"

Kaecilius shrugged. "Yes, at times. But also more otherworldly threats, when necessary. When a sorcerer has no other options, such as when they face an enemy that cannot be killed, then containment in a place where they cannot harm anyone is the ideal solution."

"Have you ever had to d-do that?" Harry asked. "Seal an enemy in here?"

"Me? No, I haven't," his teacher answered. "Thankfully. Even for a truly evil soul, being trapped in the mirror dimension would be a terrible fate. Have you yet noticed that everything is not exactly right here?"

Harry nodded. "Sometimes I see c-cracks in the air, and an object isn't quite the right size or sh-shape."

"Precisely. While we are training here, I am keeping everything around us mostly true to life, but my control is not perfect even this close. And the further away from me you move, the more space will distort and fold in on itself. If you were to walk down the street, the road would start to curve away from you, or diverge into two diagonal streets, or flip upside down completely. This is why we work so hard on your control before we can work on other magic, so that you can come in here without me in safety."

"And people can g-get trapped in here?" Harry asked with horror.

"Yes. Generally, there are only two ways out of the mirror dimension. First, the person who created the entrance can keep it open to come and go as they wish. If they bring someone with them, their companion can leave if physically accompanied by the original caster. But if that entrance closes, the only way out is a sling-ring portal."

"Which I can't use," Harry flatly said.

Kaecilius tilted his head. "For now, yes. I am still researching the magic of the portals, and I believe it may be safe for you to open one as long as you do not touch it. I am not completely sure, however, and I would rather not bet your impressive protection spell on a hunch."

Harry felt like rolling his eyes at Kaecilius' paranoia, but elected to continue their discussion. "So the mirror dimension is also a p-prison?"

Kaecilius nodded. "Essentially. But because the mirror dimension is the same size as the real universe, the odds of meeting one of those who have been confined here are remote."

Harry noticed his teacher had a strange look on his face when he said that last bit. "Have you ever met anyone?" he asked.

Kaecilius nodded, looking a bit embarrassed. "Once, from a great distance. It was last fall, as I was traveling. I had been using the mirror dimension to move further by folding space as I walked, and I came upon Darjeeling near the border of India. There was a mighty power at work there, using the city as a template to build an enormous throne. The buildings and roads were reshaped and molded in colossal shapes, then stacked upon each other. I could see a huge being with eight arms orchestrating the construction."

Harry was fascinated. "What d-did you do?"

"I created a portal and ran before they could see me, of course," Kaecilius answered.

"You what?" Harry asked, dumbfounded. "You ran away?"

His master shook his head. "Absolutely, and that is exactly what I expect you to do if you meet someone in the mirror dimension. Apparate back to the entrance you created, come back to the real world, and shut the entrance immediately."

"I'm n-not afraid," Harry said, affronted.

Kaecilius stepped closer to Harry and looked him squarely in the eye. "It's not about being afraid," he said slowly. "It is not cowardly to run from a fight that you don't need to start. Whoever that being was, they were immensely powerful, reshaping the mirror dimension in that way. Someone had obviously trapped them there. Had I engaged with that being, all I would have accomplished was the possibility of them stealing my sling ring and returning to our world, and I probably would have been killed in the process. They couldn't hurt anyone in the mirror dimension, so I left them there. Do you understand?"

Harry huffed, but nodded. Kaecilius seemed to accept that as an answer and continued, "So the reason I train you this hard is so you can defend yourself in a worst case scenario. If you are in the mirror dimension alone and you find yourself trapped by one of its prisoners, their most likely form of attack will be to manipulate the world around you in a violent or destructive manner. They will seek to imprison you in the ground or smash you with a building, or perhaps distort the dimensions of your surroundings so much that you become disoriented. It is therefore vital that you can fight back in the same way. The odds are that you will never face such a threat, but you have quite a propensity for finding danger. Better safe than sorry, yes?"

Harry nodded again, this time feeling more motivated, and Kaecilius seemed satisfied. He took Harry by the shoulders and guided him through the prism-like entrance back into the real world.

"Let's break for lunch, and you can answer some of the letters you've received," the man said, pointing to Harry's desk. Hedwig was sitting calmly on her perch nearby, looking like she'd just come out of the wind. Harry scratched her brow fondly, causing her to bark in pleasure, and he sat down to look over his mail while Kaecilius disappeared through a portal. One envelope had Ron's characteristic untidy scrawl, while the other had his name in an elegant cursive on one side, as well as a wax seal with the letter M impressed upon it. Clearly, Malfoy had followed up on his request to write.

Harry decided to read Ron's first, as he had a feeling Malfoy's letter would give him a headache. He opened the envelope and unfolded the letter.

Dear Harry,

How are you? I hope the muggles are leaving you be, and your teacher isn't being too hard on you. He sounds like a decent bloke from what you've told me, but I know you said he was mad at you because of the whole Chamber mess. Don't let him work you too hard.

I'm certainly working harder than usual. What with me, Fred, and George being petrified for half the year, mum is trying to cram months of lessons in our heads as fast as we can. Since Ginny was in such a bad state for most of the year too, she's been sitting in on most of our lessons. It's been exhausting, mate! At least we don't have to do any chores while she's teaching. Don't tell her I said, but mum is so busy that we've been mostly just eating sandwiches for every meal, even dinner! Hopefully, we'll all be ready for next year in time. Well, even if we're not, at least I'll have Hermione to help me.

Oh, and I almost forgot to tell you! Dad won the big sweepstakes for the Daily Prophet, and we even got our pictures in it! I put a clipping in the envelope for you to see. We were going to visit Egypt where Bill works with the winnings, but with all our extra lessons, Mum just put the money in our Gringotts vault for safe keeping. She says I can get my own wand when we go school shopping so I don't have to keep using this hand-me-down.

Hope to hear from you soon!

Ron

Harry peeked in the envelope and took out the newspaper clipping. It was dated to a few days previous, and proclaimed in large letters, "MINISTRY OF MAGIC EMPLOYEE SCOOPS GRAND PRIZE!"

Underneath the headline was a moving picture of the Weasleys smiling and waving in front of their home, the Burrow. The eldest boy still at home was Percy, who was trying to look dignified with a small smile, waving like the Queen did at parades. The effect was completely ruined by Fred and George, who were taking turns giving him bunny ears and mimicking him behind his back. Ginny was beginning to look more lively since the disaster of the previous year, but her mother clearly had a strong grip on her shoulders, as if frightened that her daughter might disappear at any moment. Ron was in the center of the group with his father behind him, and Harry could even make out Scabbers, Ron's rat, sitting on the boy's shoulder.

Harry couldn't be happier for them, fondly remembering how they'd basically adopted him last summer. He hoped they made the money last.

At that moment, Dobby popped in with a tray of sandwiches, setting them down next to Harry. The boy smiled at his elf, asking, How is my aunt treating you, Dobby?

The little creature scowled. "Dobby has nothing to do, Harry Potter! Dobby asks and asks for chores from Mrs. Turdsley, but she says Dobby has done them already!"

Harry grinned, but then a thought struck him. Dobby, he said. Do you know where the Weasleys live?

Dobby nodded. "The great Harry Potter went there last year for a month, and Dobby watched him when possible."

Excellent! Harry replied. If you go there when you're bored, I know Mrs. Weasley is too busy to cook and clean this summer. I bet she'd love it if you helped out.

Dobby's ears went straight into the air. "Harry Potter means it!? Dobby can go clean the Weezy's house for them?"

Absolutely, but you must take a break when you feel tired, all right? Harry said, looking at his elf sternly. That is an order.

Dobby nodded excitedly and popped away.

Harry smiled, feeling like he'd accomplished his good deed for the day. He reached for Malfoy's letter and broke the wax seal, then pulled out a letter printed on what felt like very expensive parchment.

Potter,

Thank you again for agreeing to write me. In reviewing my behavior during our first year, I began to realize how terribly I treated you over a very small slight. When we first met on the train before we were sorted, I insulted the family of Ronald Weasley, and I believe that must have coloured your impression of me from the beginning. I apologize for that, especially as you had no way of knowing the bad blood that lingers between his family and my own.

Several generations ago, a witch betrothed to my ancestor broke her contract and eloped with one of Weasley's ancestors. After a lengthy court battle, the witch was allowed to stay with her new husband, but the Weasleys lost much of their fortune and their seat on the Wizengamot in damages. Our families have rowed ever since.

I should have realized how my behavior looked to you that day, since this was not information you would have known. Instead I took your rejection of a handshake very personally. I hope that when next we meet, you may take me up on a similar offer.

I hope your summer so far has been pleasant. I know that you live with muggles. I wonder how much their lives differ from wizards. Perhaps you have insight on the subject?

Feel free to write whenever you'd like.

Sincerely,

Draco Malfoy

Harry had been right. He had a headache just from reading that. Everything Malfoy had written seemed so… professional and reasonable. His explanation of their first meeting gave new context to everything that had happened, and Harry honestly felt a little guilty about how he'd reacted now. There had been no insults towards Harry's relatives in the letter, and the Slytherin had basically apologized for everything.

But Harry knew better than to trust it. He had no doubt that every word had been proofread by Malfoy Senior, and it had all been carefully crafted to appeal to Harry. He would play the part just like Draco, and maybe he'd learn a few more new things.

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July 2

As soon as Kaecilius arrived the next day, he waved his hands in the familiar pattern and threw Harry and himself into his student's mind. Harry took a few moments to orient himself and give himself a body, then glared at his teacher. What was that for? he asked angrily.

I believe I have avoided the subject long enough, Kaecilius said. Now that you can be trusted in the mirror dimension by yourself, we should discuss the trip you took into your mind with that… monstrous person.

Harry tried not to wince. He had known the subject would come up eventually, but he'd tried to avoid it for as long as possible. Yes, sir? he responded, sounding as meek as he could.

Kaecilius gave him a knowing look. Yes. First, you will show me the memory of it. Call it up. ALL of it.

Harry sighed, but obeyed, giving his master the full memory and waiting for the man to finish viewing it.

After a few minutes, Kaecilius seemed to shake himself awake, then glowered at Harry. You foolish boy, he growled. It is pure dumb luck that you aren't trapped in that chunk of memories to this day. If you hadn't found a memory to grab onto, you'd probably be so overwhelmed by those horrible emotions that you were driven mad.

Harry gulped, knowing the man was right. Yes, sir. Sorry, sir.

That's not the worst of it, his teacher said. Riddle was surprised you escaped, you remember? He thought you'd be trapped.

Yes, Harry answered. So?

Kaecilius looked furious. So? What was he doing to Ginny the entire year, you simpleton?

Harry gasped. He was… possessing her!

Exactly! And you very nearly gave him an empty human vessel to use as he pleased! He'd have been walking around in your skin and no one would be the wiser!

Harry felt nauseous at the thought. One of my friends would've noticed, he protested weakly.

Not necessarily, his teacher countered. Riddle would have access to your every memory. He could have passed himself off as you quite convincingly, I'm sure. I would notice as soon as I was in your mind, but we weren't together all year. By the time we were due to meet, he could've easily absconded to who knows where.

That was a less than pleasant thought. Harry remembered how in the chamber Riddle had claimed he could run off and resurrect the older Voldemort. The world didn't need one Dark Lord, much less two.

You're right, Harry admitted, feeling extremely foolish. I really messed up. He just seemed so nice and helpful.

Something you need to understand, Kaecilius replied. Is that nice is different than good. Now, we should discuss what you actually viewed in that memory.

Harry perked up. The flight tattoos?

Kaecilius nodded. Yes. Overall, it seemed fairly simple. Mayan symbols in the proper alignment, activated by an incantation. It appeared to be controlled by thought and willpower, and I'm sure it is quite magically draining.

Can I do it? Get the tattoos, I mean? Harry asked hopefully.

His teacher looked at him assessingly. Now? No. You're not even 13 yet, and Mayan rituals tend to have unforeseen side-effects, especially on those still growing. I traveled to Belize in the winter, and met with several different priests and shamans while I visited. One of them performed a ritual for breathing underwater when he was a teenager. It worked perfectly for several years, then one day he woke up with scales covering his body.

Scales? Harry responded, disgusted. Like a snake?

They looked more like fish scales, actually, Kaecilius said. Silver and iridescent. Quite beautiful on a fish, but not on a human. You understand why I am cautious about the tattoo now?

Harry nodded energetically. I don't want to end up looking like Hedwig.

Precisely, Kaecilius answered, smiling proudly at the boy. I will research possible effects the tattoo could have on you. Perhaps we can look for another memory during this summer. We'll look together, yes?

Harry nodded again, then looked up at his master gratefully. Thank you for helping me, sir. I would probably have tried the tattoo without thinking about it otherwise.

Kaecilius smirked. Yes, you probably would. And at your age, I probably would have as well. The allure of flight is quite strong. Now, let's leave your mind and practice awhile in the mirror dimension, yes? I think you need to prove your repentance for the idiotic decisions you made with Riddle's book.

Harry groaned. This would not be fun.

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July 15

"BOY!"

Harry sat up in his bed, instantly awake. Kaecilius had worked him hard all day, both with mental and physical exercise. While Harry had been in decent shape from Quidditch, Kaecilius seemed to be unsatisfied with his lean form. Workouts of all kinds had been interspersed with exercises to improve Harry's magical control, and the end result was an exhausted young wizard.

He groggily got out of bed and looked out the window at the setting sun. While Dobby was helping the Weasley's, Harry had to deal with his relatives all alone. He took a deep breath and started downstairs.

He entered the kitchen to find his uncle standing by the phone. The man looked at Harry like he was something unpleasant on the sidewalk, and said, "About ruddy time you get down here! Your Aunt Marge will be coming in a few weeks, and that means this place needs to be spotless!"

Harry looked around himself. Dobby had worked wonders. While Aunt Petunia had always insisted on a clean household, now everything gleamed. Being able to clean things magically meant that the floors, counters, and appliances looked brand new, and Harry knew that the rest of the house was the same. He looked back at his uncle. "All right…?" he said, nonplussed.

Vernon seemed to realize what Harry was implying, and swelled up indignantly. "Don't get smart, boy. Your aunt runs a tight ship and doesn't let you slack off, and that's the only reason this place hasn't gone to the dogs! Now you'll be fixing up the guest bedroom so it sparkles, and making sure her dog Ripper has a nice new doghouse out back. The old one has fallen apart, and you're to build one with padded flooring. Ripper's got arthritis these days, apparently."

Harry kept himself from rolling his eyes with difficulty. Ripper was a mean-spirited and badly tempered bulldog who should've been put down years ago. Harry normally liked dogs, but he made an exception with Aunt Marge's 'sweetums'.

"Yes, Uncle V-Vernon," he replied.

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July 20

Harry wiped his brow and heaved a tired sigh. Ripper's doghouse was almost built. His uncle had bought a feather-filled bed that would placed inside, and it was honestly nicer than the mattress in Harry's room. He was sure Ripper would tear it to shreds immediately.

It was as he hammered in the final nail that he heard a quiet "woof" come from behind him. He turned around and came nose-to-snout with what looked like a giant German Shepherd. It was completely black with green-yellow eyes, and its tongue lolled out of its mouth in a pleasant way. "Hello," Harry said quietly, hoping it was a friendly dog despite its size. After all, Hagrid's boarhound Fang was a huge teddy bear, and Ripper, while small, could've been previously owned by Satan judging by his temperament.

The dog wagged its tail and lowered its front paws, clearly hoping to play. Harry smiled in relief and looked for a stick to throw. With a quiet pop, a bright red ball appeared in Harry's hand. Harry and the dog both jerked in surprise, but then Harry realized what had happened. "Thanks, Dobby," he murmured, and then tossed the ball across the yard.

The dog stared at Harry for a few more moments in silent confusion, then turned and took off running after the ball. Harry laughed as the rubber ball seemed to elude the dog's jaws several times as it bounced before it was finally captured and returned. The dog dropped the ball at Harry's feet and panted happily, and Harry scratched its head. "Where did you c-come from, boy?" Harry asked, then took a quick peek to check if he was right. Yep, definitely a boy.

The dog panted a few more times and then pawed at the ball, clearly asking to play some more. Harry threw it and watched as the dog took off running again. It had no collar, but its fur was well trimmed and clean, so Harry doubted it was a stray. He threw the ball a few more times, but it was beginning to get dark and he was sure that Dobby would want to cook dinner, which meant Harry needed to hide in his room for awhile. The next time the dog returned the ball, Harry said, "I have to go, boy, so you head b-back to your family, ok? How'd you even g-get in here?"

The dog wagged its tail and licked his hand, then took off for the back fence in the yard. It squeezed between two bushes and Harry saw it slip under a missing board in the fence. He heard the click of its claws on the alleyway behind the house, and then it was gone.

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A/N:
Subtle changes from canon in this chapter. The changes are there for a reason!
Regarding Draco Malfoy, I made some changes for a few plot reasons, but also because his character in the original books never made sense to me. The boy is held up as the epitome of Slytherins, but for the first 5 novels at least, he is the most impulsive, brash, and Gryffindorish Slytherin in his house. I wanted to change that in this story. Here, Draco is a very sneaky snek.

I hope you enjoyed the chapter! Please review and let me know what you think!