As Ron, Hermione, Luna, and I walk into the Hogwarts Entrance Hall, a flustered Professor McGonagall hurries over to us.

"Good, you're here. Mister Potter, Miss Lovegood, you two are to report to the hospital wing. Miss Granger, if you could come to my office, then we can work out some final details on your schedule."

"Hang on," I object, "why are Luna and I going to the hospital wing?"

"Madam Pomfrey has demanded that all students who passed out when the dementor entered the train are to report to her for a basic health checkup. If she determines that no one suffered acute effects from dementor exposure, you'll be free to return to the feast. Now, I trust you two to make your way up there on your own. Miss Granger, with me, please."

"Is this really necessary?" I shout after her.

"Yes!" She shouts back. "Now go!"

I see that Minerva's still a hardass, even all these years later. Some things never change, I guess.

'You knew McGonagall?'

Yeah, she was the Gryffindor girls' prefect in my year. She was a total stickler for everyone else following the rules, even though she frequently broke them herself. The two of us never got along, really.

'…Huh.'

What?

'It's just… I forgot how old you are, since you always look like a teenager in my mind.'

You don't get to call me "old". Technically, I'm only a young adult. I have memories up until I was eighteen, but while I was stuck in the diary, I lacked the external stimulus to age in the way a conventional mind would. For all intents and purposes, I am a temporally displaced teenager.

'That is equally weird, frankly.'

Oh, shut up.

Luna speaks up before I can think a snarky reply back to Tamelyn.

"Are you having a discussion with the voice in your head?" She asks as though it was a perfectly normal thing to ask a stranger.

"Erm… what?" I reply. I have no idea how I should respond to a question like that, even if it wasn't an eerily accurate guess.

Luna appears nonplussed by my hesitance. "Oh, you had the look on your face that most people get when they're having a conversation, but since you weren't saying anything out loud, I assume that you must have been speaking in your head."

"That's an… interesting assumption, Luna."

"I try to speak to the voices in my head all the time, but nothing they say ever makes sense. You looked like you were only talking to one person, though."

"…Right." This girl is clearly several players short of a full quidditch team.

Not going to justify her question with a response, Harry?

'Absolutely not. Fewer lies told means fewer stories to keep straight.'

Good, you're learning.

'Shut up. You're a terrible influence.'

I am, aren't I?

I hold in a sigh as Luna and I approach the hospital wing. Inside, I see Ginny Weasley, Theodore Nott, and several upper year students I don't recognise. Madam Pomfrey is moving from one patient to the next, handing out chocolate to everyone and running through several diagnostic spells on each patient.

'Hey, Tamelyn… She won't be able to detect you, will she?'

Not unless she casts the extremely obscure horcrux revealing spell on you. The only other way someone could detect me is if they know to look for a second presence inside your mind and are able to break down my occlumency barriers. I'm basically undetectable unless someone already knows I'm here. You may have slightly elevated readings of dark magic, but since you're not a traditional horcrux, it will be much weaker when compared to any of the others I would have made.

'Okay, cool. How would someone look for you inside my mind, anyways?'

Legilimency. It's what Dumbledore did to you last year after the ritual I performed in the Chamber rendered you unconscious.

'What is it, though?'

Think of it like mind reading. It's a way more complex discipline than that, but one of its many capabilities is allowing its user to browse the memories of their target. I wouldn't worry too much about it, though. It's a very rare skill, and on the off-chance that someone does look into your mind, then I'll let you know.

'What about my memories of interacting with you, though? Couldn't those be read, as well?'

The oath you swore protects them, and I've been occluding the incriminating ones that don't involve me. I'm not an idiot, Harry. Still, it wouldn't be a bad idea for you to start learning occlumency on your own. While my mind is all but impenetrable, I don't think I could effectively occlude your memories if I were to "fall asleep" while you were still awake. It would also be good to have some additional defences guarding my secrets beyond the vow you gave me.

"Mister Potter!" Madam Pomfrey's sharp voice cuts through my reverie. "Are you alright?"

"I'm fine, Madam Pomfrey." I reply curtly.

"Are you quite certain about that? I was trying to get your attention for a few minutes before you answered!"

"I've had a lot on my mind, ma'am."

"I'll be the judge of that!" She says as she begins running through diagnostic spells. "Hm… you're less malnourished than you were after the last two summers. I don't know why Albus is so insistent on sending you back to that place… Let's see, moderate dark magic exposure, higher than average adrenaline… Well, you're not doing too badly. I'll be keeping you up here with the others for a few hours."

"What about the start of term feast, though?" I protest.

"The house elves will bring food up here! Now get into one of these beds or so help me…!" She snaps.

She's got great bedside manner, huh?

'I think she's just had to deal with far too many people who ignore her. You know how teenagers are.'

Unfortunately, I do. I'm living inside one.

'Hey!'

'I hope you're happy.'

You have no idea how happy I am. This exceeds my best expectations.

'The worst part is that I think your sense of humour is starting to wear off on me.'

Oh, so you're having fun here, too? And you thought this was a bad idea.

I half-laugh, half-sigh as I watch a drunken Professor Trelawney shamble about the classroom, predicting death and despair for all present.

'You are a terrible influence.'

To think, all I had to do to corrupt the great Harry Potter was start exposing him to morbid jokes.

'Shut up.'

"You, there!" Trelawney says as she points at me. "You have an aura of darkness and despair around you!"

'She's actually pretty spot on for that one, even if my "aura of darkness and despair" is your doing.'

Stopped clocks are right twice a day, Harry.

"You are a child of destiny! The world's balance swings around your fate! I fear that one such as yourself is not long for this world! You shall die before you come of age! Maybe even more than once! The Fates swirl about you in such an odd way…"

Ahahahahaha! This is great! I expected a class, but I got a comedy routine! Oh, I am going to love Thursdays!

'You are a terrible influence!'

I can feel you struggling to hold your laughter in, you know.

'Yeah, yeah, but I can't let you get an ego about this. You've got enough of that already. And I'm still mad that I'm losing an opportunity to pursue academics in favour of this spectacle.'

Yes, yes, now let's see who her next target is…

Trelawney shambles over to Parvati and begins predicting her rise as a Dark Lady, which leaves Parvati appropriately horrified.

I think I have a new favourite class.

"Well that was worthless!" Hermione huffs. "Honestly, how is she even a teacher!? She did nothing but predict negative events, and she predicted that you would die multiple times before reaching the age of seventeen! What is wrong with her!? It's an insult to the principles of education!"

"I thought it was pretty funny." I remark.

"Really, Harry?" Ron asks. "I mean, she said you'd die. I thought you'd be moodier about that."

I shrug. "I would be moody if I thought I was actually going to die. I didn't believe a word she said, though. The class was hilarious just because of how melodramatic she was."

"Classes aren't supposed to be hilarious!" Hermione protests. "They're supposed to be learning opportunities!"

"And this class is clearly the former and not the latter." I counter. "Honestly, if you don't want to be there, just drop the class."

A look of horror crosses Hermione's face at the prospect of dropping a class. "No. No, I'll suffer through it. I won't let her win."

She does realise that the quality of a class is not an intentional affront to her, personally, right?

'I wonder sometimes…'

As we make our way into the transfiguration classroom, the atmosphere in the room makes it quite clear that most of the class did take the drunken teacher's words to heart. I realise that I'm likely the only student in the class who found humour in the experience. McGonagall takes notice of the mood in the room and addresses it head on.

"Alright, what exactly has rendered this whole classroom so morose?" She asks.

The Gryffindors all mutter some variant of "Professor Trelawney" in response.

"Oh dear." McGonagall sinks her head into her hands. "What did she do this time?"

"She said my love of gossip would lead to me being a Dark Lady who controls information!" Parvati squeals.

"She said I'd die at least once before reaching the age of seventeen!" I say with a laugh.

"She said I'd become best friends with Draco Malfoy!" Neville shudders.

Malfoy shoots Neville a glare, obviously peeved by having his friendship put on the same level as dying.

McGonagall sighs. "Yes, she does like to make highly… eccentric predictions, if one can call them that… No matter. She does this every year, and not once have any of her predictions come to pass. You may all disregard everything she told you. I do recall advising against taking the class at the end of last year, you know."

'I don't remember that.'

It was probably when you were in the hospital wing.

'And whose fault was that?'

Yes, yes. It didn't work out spectacularly for either of us. Be fair, though, it could have been much worse. Imagine if I had actually missed the soul shard in your scar and just sicced Tessie on you. You probably would have died in some hilariously dramatic fashion.

'I'd like to think I would have found some miraculous way to survive…'

And you are free to keep thinking that, no matter how unlikely it would have been. Now get to work on your transfiguration before Minerva realises you haven't been paying attention.

I pull my mind from my thoughts and begin attempting the transfiguration. Transfiguration has never been my strong suit, since I struggle with the visualisation aspect. As I work, though, I can feel Tamelyn occasionally nudging my thoughts in the right direction, improving my focus on the work.

After I complete the assignment, I look around the room to see that everyone else (sans Hermione) is still working.

'Wow, I've never finished this quickly before.'

Your mind wanders a lot, and you're good at overthinking things. Both are a hindrance to transfiguration. It shouldn't be a surprise that you do better with me guiding you.

'Yeah, yeah. You're absolutely amazing at everything. Your modesty is noted.'

Much as I love being praised, I had similar issues at first. It wasn't until after I learned to engage in periodic meditation that I was able to focus well enough to excel at the field. Dumbledore was, predictably, incredibly suspicious of my sudden leap in skill, so I frequently had to get my Head of House to confront him about my assignments being underscored.

I find myself wondering if I could go to McGonagall and have her do the same thing about Snape. He certainly has a similar grudge against me, after all. At the same time, I'm not sure how much I trust her to help me after how the previous years have been handled…

As I leave charms class, I mull on how poorly it went compared to transfiguration. We practiced the water conjuring charm, and every time I attempted it, the water came out with the force of a firehose. Flitwick told me I was overpowering the charm, though I had no idea how to fix that.

I told you our cores were combined. All your spells will be more powerful.

'I didn't have any issues in Transfiguration!'

Of course you didn't. Overpowering a transfiguration just makes it transform faster and last longer before reverting. Charms and combat spells have a stronger effect when overpowered.

'You never did explain what a core is, either.'

That's… Well, I can't honestly blame you for not knowing what a core is. It's actually a founding principle of soul magic, which is considered too "taboo" to study. Any reference to the term you'd be able to find would just be pureblood propaganda.

'So, what is it? It obviously relates to magical power.'

It does. Kind of. Purebloods like to think that it's an organ they have that muggles lack, and that it's where they get their magic. They also tend to believe that stronger bloodlines mean larger cores and all the typical stuff that accompanies their distinct brand of bullshit.

'You're a lot less on-board with the whole "blood purity" thing than I would have expected.'

People with power believe in blood purity. It only made sense to pander to them while using their power to fulfill my own agenda. That was my plan once I began amassing influence, and while I thought the purity aspect was stupid, there was actually enough overlap in our goals to make using them convenient. Anyways, cores. The standard idea of a core is, obviously, nonsense. There's no organ that makes one magical. The truth is that magic comes from the soul. What people think of as being a "core" is actually the soul's ability to process magic into a usable form.

'So, the core is a part of the soul?'

No, the core is the soul. Magic is absorbed through the environment and processed by the soul into a usable form that it then stores for later use. It's a multifaceted concept, but magical strength can generally be broken down to three ideas. The first is the storage capacity of the soul, how much magic it can store. You and I both have an above average storage capacity. Next is processing rate, how quickly the soul can intake new magic. Again, you and I are both above average in this area. The last component is flexibility, and this is where it can't be expressed simply. It's basically how easily your soul can convert magic into certain spells. So, you excel at all forms of combat and defensive magic, and probably the dark arts as well.

'Hey!'

Don't shoot the messenger, Harry. If you're good at combat magic, you'll almost certainly excel at the dark arts. The thing is that affinities are fickle. A person's affinity basically determines the ease of casting a spell on a case-by-case basis. Some people excel at certain types of elemental magic, others at entire fields of magic, and some on all spells that can be applied a certain way. You're a rare case in that you have a broad affinity for an entire field of magic, probably a side effect of having a part of me inside your head in tandem with your abysmal upbringing.

'So living with the Dursleys gave me an affinity for the dark arts. Great.'

Hey, it's an educated guess, not a guarantee!

'So I'll always be better at combat spells than anything else?'

No, it just means they'll come more easily to you. Affinities are not static, and change along with your goals, values, personality, and all that. You can also alter your affinities if you practice magic that's hard for you. Eventually, you'll be able to use it as easily as you would any form of magic that you're naturally good at. Most people don't do this though, which is why almost everyone tends to specialise. So long as you don't put undue stress on your core, continually using magic makes you better at magic.

'Does that include the storage and regeneration capacities, too?'

Actually, yes, it does. The mere act of using magic makes you slightly better at using it in a general sense. It takes a very long time for those small increases to have any noticeable effect, but they add up over time, hence why older wizards are often terrifyingly powerful. By comparison, affinities are much easier to train.

'Hang on, though… You said that the soul is what determines the strength of one's magic. Didn't you split your soul, though? Wouldn't that weaken you?'

Ah, yeah, the horcruxes.

'Horcrux?'

Shush, I'm about to explain. See, the soul is always treated as a complete object, no matter how many pieces it may be in. So, as long as part of the soul is bound to the world, any remnants of the soul will be prevented from passing on. A horcrux is an artefact that has a part of a soul bound to it, so that the main soul cannot pass on. Technically, any horcruxes with a will could persist as well, should their container be destroyed, though I'm probably the only one in history who could do that. Imbibing a horcrux with will is no easy task, after all. Any other soul fragments without a will to persist would dissipate and fade into limbo.

'You still didn't explain why splitting the soul doesn't weaken you.'

Oh, right. As I said, a divided soul is still considered a complete object. So, even if the soul is in multiple containers…

'…You can still draw on its full strength.'

Exactly, so long as all the parts are bound, at least. I couldn't draw on my core self's power, since she's just a wraith, but I can use the strength of all the other fragments.

'So, my spells are coming out too powerful because…'

Because your soul is bound to that of an adult witch of above average power. Your magic is over twice as strong as it was before., possibly even moreso

'So, how do I fix it?'

By doing something you should have done ages ago: learn occlumency.

As Tamelyn gives me instructions on how to reach a hidden room on the seventh floor, I ask the question that's been bothering me.

'Why did you tell me about horcruxes? Isn't the secret to your immortality the kind of sensitive info that you wouldn't want people knowing?'

You swore a binding magical oath to me not to reveal my secrets. It binds you from making any slip ups and it prevents the secrets from being picked from your head by a legilimens. The only way to break your oath to me is to do it intentionally, at which point, it will kill you. Also, understanding how horcruxes work will be vital to helping you learn to regulate your power. Not only will you be able to restrain the power of your spells at will, you can overpower them as well.

'Like that cleaning charm you did? Back at the Dursleys?'

Yes, like that. Ah, hang on, there's the tapestry. We're here.

I look around the corridor. There are no signs of any secret rooms, just a hideous tapestry of a wizard trying to teach trolls to dance.

You'll love this. Watch.

Tamelyn shifts into control of my body and paces back and forth across from the tapestry.

I need a location perfect for occlumency meditation.

As she makes her third pass past the tapestry, a door fades into existence on the wall across from it. Tamelyn confidently strides over and opens the door, revealing a minimally decorated room with several mats in the middle. The corners of the room emit a dim orange glow that has the same colour as the torches that light the rest of Hogwarts, but lack the distinctive flicker of flame.

Yes, this is perfect. I love this room. I found out about it in my seventh year at Hogwarts when I was using legilimency to pick the minds of the school's house elves for information.

'What does this room do?'

As far as I was able to tell, whatever you want it too. I never got a lot of time to test the limits of what the room could and couldn't do, unfortunately. Dumbledore was stalking me throughout most of my seventh year, and I didn't dare lead him somewhere as useful as this.

'That's sensible'

Yes, now, let's get started. Take a seat on one of those mats and get comfortable; I suspect we'll be here for a while.

I cross my legs and take a seat on the mat, shifting around a bit until I feel comfortable.

Okay, good. Now, occlumency has several aspects to it, but before you do anything, you need to discover the boundaries of your mind. I'm going to completely block myself off from you during this step, since the boundaries between us blur every time we communicate.

'Alright, so what do I need to do?'

Since we're connected, you may find some of this easier. Our minds are pressed right up against each other, so if you can find my barriers, you should be able to extrapolate the complete boundary of your mind from the shape of the boundary between us.

'Shape? Seems like an odd choice of words.'

The words to explain the workings and properties of the mind don't exist. Now, focus on clearing your mind of stray thoughts while using magic to feel the edges of your mind. I'm shutting myself out now. Good luck.

If Tamelyn hadn't been in my head for months, I don't think I would have known where to get started. Fortunately (or unfortunately; it's been hard to keep track of how I feel about her), her constant presence has given me a general feel for the magical aspect of the mind.

I start by moving to the "area" of my mind where she is when she speaks to me. Instead of feeling "her", I feel a "wall" that blocks me off from her. I follow along the "wall" to the point where it ends. From there, I can feel a very vague "boundary" that I focus on following. It's hard to follow the boundary between "thoughts" and "non-thoughts", since thoughts aren't tangible things in the first place. I trace the border several times, trying to memorise and solidify my understanding of where it is for several hours before I take a break.

Once I stop, it doesn't take Tamelyn long before she pipes up.

Well, I hope you didn't waste the whole time period. How did you do?

'Alright, I think. I mostly just sort of traced the border to feel it out.'

Alright, that's good. You probably could have started the next step if you were able to do that much, though I wasn't able to tell you how to proceed, so whatever. Try to continue the "border tracing" without actively meditating in the future — that's the basis of creating barriers, though you obviously aren't at that step yet. We'll do another meditation in a few days.

Potions class is as unbearable as ever. Snape's unhelpful attitude towards teaching, his constant rude comments, and his constant leering make being in the classroom with him a highly unpleasant experience. The awkwardness comes to a head when I turn my assignment in for the day. As I make eye contact with Snape, I feel an odd brushing sensation at the edges of my mind. I quickly break eye contact and move back to my desk.

'What was that?'

Oh, you actually felt it? That's good — I'll make a proper occlumens out of you, yet. Snape was trying to browse your thoughts, though you severed the connection pretty quickly.

'Wait, what!? He didn't see anything, did he?'

Of course he didn't. Remember, oath? I also covered up the memory of you stealing ingredients for the polyjuice potion you made last year. You're welcome.

'Is it normally possible to do that? Guard someone else's memories?'

Of course it isn't, but nothing about our situation is "normal". Technically speaking, our situation is "impossible". Human horcruxes are impossible, as is the idea of two souls sharing a body without decaying the body in the process. By all rights, we should either be in a state of partial possession and find ourselves at an unstable equilibrium that would eat away at your body, or we should have entered a contest of dominance in which one soul is destroyed by the other. The two of us coexisting peacefully should not have happened.

'I wouldn't call our coexistence "peaceful".'

Fair point, but my point still stands.

'So partial possessions cause the body to decay?'

You did see what Quirrell looked like at the end of your first year, right? Before you burned him to ash, that is.

'They were both pretty gruesome.'

Well, what he looked like before you burned him is the usual result of a partial possession. It's also something that is somehow not happening to the two of us. I blame your soul ward. That thing is weird.

'I'd say I'm happy with the current situation, given that I am neither dying nor dead.'

Some hero you are. You were more than willing to jump in the path of danger last year to save the damsel in distress. Why not do it again for me?

'Because you are in no way a "damsel in distress". Damsels in distress don't try and kill people or possess them.'

Hmph. Fine, have it your way.

A/N: Lots of Harry/Tamelyn conversations in this chapter. There will be a fair amount of those for a few more chapters before I start gradually diverging more heavily.

Trelawney's predictions for Neville and Parvati are a dig at my other fanfic, Harry Potter and the Scrambled Sorting.

Magical cores are a concept that many dislike, and not without reason. Most of the time, it's just a lazy way to say "x character is super strong". For this story, I used a more dynamic explanation that felt natural to me. I don't know if any similar explanations have been done before, though. I only really used the term "core" because I didn't feel like coming up with a new term when fanon's given me one already. This explanation will probably also be canon for Harry Potter and the Scrambled Sorting, though I doubt I'll include a description in that work.

The idea of the soul being treated as a single object even when divided was borrowed and slightly modified from The Historical Importance of Runic War Warding in the British Isles, a fem!Harry/Voldemort fic that is probably the best fic with said pairing.

E/N (Xgenje): I honestly like the way a lot of the mechanics are fleshed out here. Can't wait for the actual fleshing out later!

Also Bwahaha little evil dark lordy Potty.