Disclaimer: I am not J. K. Rowling. I don't own Harry Potter. Nobody pays me to write this.

Warnings: Brief mention of slash; Armageddon; muggle bashing; a little angst; language

Author's Note: This one just came to me last night and I wrote almost all of it in one sitting. It's… quirky.

2020 (Global Population: 2)

Everyone was dead.

The muggle World War III had started with soldiers. Then there came the bombs that leveled cities and poisoned the world with radiation. That's when the magicals had gotten involved. When we finally realized that the muggles we so underestimated were destroying the planet on which we all had to live. Things just went downhill from there.

The muggles panicked when they became aware of the fact that magic was actually real and was being used against them. They bombed their own people when there was a suspicion of a magical family living in the vicinity. We fought, but they were so many.

Magical Britain's contribution to that war was laughably non-existent. We were too busy fighting our own war. Well, Voldemort did his part to kill as many muggles as possible – long before any magical nation had actually decided to do any such thing. And I devoted myself to fighting him and protecting muggles. Because fighting him was what I'd been doing my whole life and protecting muggles was just what good little heroes did.

And then came the plague. Genetically engineered to kill only magical humans. Again, we fought back, mutating the plague to attack muggles.

In the end, it killed everyone, mutating on its own more quickly than cures could be manufactured. Magical creatures were some of the last to go, but they died too. Everything with a touch of magical blood. Even vampires did not prove immune to the ever-mutating virus.

Everyone died.

Except me.

Well, me and him. Of course. It had always come down to the two of us, hadn't it? Good and evil. Gryffindor and Slytherin. Right and wrong. Mercy and malice. Light and Dark. We were as disparate as two people could be.

And yet we were the same as well. Both incredibly powerful. Both shaped by painful childhoods. Both baptized in the blood of our parents.

Really, we were very similar. Our greatest differences were in our choices. Namely, the fact that he'd made his. I hadn't. I'd done what was expected of me. I'd been who I was expected to be. I'd fought who I was expected to fight.

In the end, none of it meant anything. The world fell. And not because Lord Voldemort won. It fell because he didn't win. The muggles destroyed it. In their greed. Their ignorance. Their pride. The fact that they killed themselves in the process was little consolation.

Worst of all was that I was alive. The bombs didn't kill me. The plagues didn't kill me. Thirty-seven individual suicides didn't kill me. Dueling to the death against Tom at least eighteen times didn't kill me. Couldn't. Because I was immortal.

Another similarity. We were both immortal. I was his horcrux. He was mine. And so we were trapped. The last survivors in a dead world. Forever, apparently.

2036 – 16 years

Hogwarts. My home. It was gone. Barely even rubble left. It seemed a fitting metaphor for the rest of my life.

I don't know how long I stood there before I realized that I wasn't alone. I looked across the crater at the other man standing there. I couldn't say that I was really surprised that we'd both ended up here. Once, this place had been his home, too.

I looked at the rubble again. I wondered if I could rebuild it. Maybe not the same. There wasn't any need for a school anymore, after all. But maybe it could be a new home, built on the same spot. I knew nothing about construction, but I could figure it out. I had all the time in the world, after all.

2059 – 39 years

The Library, as we generically named it was finally complete. Twenty-three years, it had taken. Of course, there had only been the two of us. He, apparently, had had the same idea as me. After fighting about it for a few months, we'd decided – very grudgingly – to work together.

Working together had taken longer than working separately would have. We'd fought about every detail of the construction from the building materials to the floor plan to the spells we'd use to accomplish it. Eventually, we'd been able to agree that dedicating the building to a collection of knowledge was both practical and served Hogwarts well in memory.

That part had taken the longest. After he'd finally conceded to teach me his wandless flight spell, we'd set off around the world. We'd spent over a decade collecting as many of the world's books as possible. Gringotts, once we'd worked our way through the wards, was one of the most complete resources. Virtually every family had kept a collection of their most prized books and family grimoires in their vaults. Then there were magical libraries across the world, including each of the major wizarding schools. Everything that was still standing. There was a lot of searching through rubble for buried personal vaults as well, and expeditions to locate hidden collections that were often mentioned in the grimoires.

As the collection grew, our floor plan was modified. The Library, as it stands now, is more than twice the size of Hogwarts. Apart from our two relatively modest apartments and not-so-modest studies, the entire thing was a library. It was at less than a quarter capacity now, but given what we'd gathered thus far, we were both fairly sure that we'd need expansion charms before we were finished collecting.

Scouring the world for books was a slow process to say the least, but it was probably better that way. Staying busy helped me to stay sane. Him too, I suspected, though I wasn't too sure how sane he was when all this started. I shuddered to think what would become of me when I ran out of things to do.

2087 – 67 years

The Library was pretty much fully stocked. Finally. I was sure we'd missed books here and there, but we were confident that we'd uncovered most of the substantial collections in the world.

I turned my attention to studying. There wasn't much else to do, and I was now in possession of more books than I'd ever imagined actually existed in the world. I never had finished school, though I'd picked up a lot in the last eighty years. I had no idea how long studying could hold my attention, but I didn't have anything to lose in finding out.

2112 – 92 years

Twenty-five years. Studying had held my attention for twenty-five years. Well, there had been breaks in between during which I'd gone out to search the world for more books or other interesting things. Or just spent a while lounging on a tropical island. The planet was becoming healthy again. The wilderness was taking over the cities, obscuring the bomb craters. We'd probably have to wait a few million years before intelligent life evolved again, but at least the world didn't look like a war zone anymore. That was… nice. Ish.

But I'd never been an academic. I'd never been much for inaction at all. I was beginning to realize that my sanity was dependent upon my ability to find something to do that had some sort of purpose behind it. That's how it started. The research.

2118 – 98 years

"What are you working on?"

I blinked and looked up from the parchments and books spread 360 degrees around me on my work table. I'd carved it without magic when I was bored over a period of about two years. It was a round table at a comfortable height to work while standing. The center was hallowed out so that I had to duck under it to get to my workspace, but I kind of liked being literally surrounded by my work.

Marvolo was leaning against the railing that separated my workspace from the rest of the library below – he had a similar space on the opposite side of the absurdly massive library. I was quite shocked, honestly. I was pretty sure it had been at least a month since I'd even caught a glimpse of him, and I was thinking around two years since we'd exchanged dialog.

"Time travel," I admitted.

His brow rose. "Are you thinking of leaving me, Harry?"

"Well… Yeah," I shrugged unrepentantly. "Though I suppose you could come too if you want."

Marvolo's brow slowly lowered into consideration as he realized that I was serious. "How long have you been working on this?"

"Couple years," I shrugged, turning my attention to a book on the opposite side of the table and leaving my back to my former nemesis.

"What kind of timeframe are you thinking?" he inquired as he wandered over to inspect some of the paraphernalia spread around the table.

"Well, it has to be at least a hundred and twenty years, or there's no point. Obviously, I'm shooting for more than that. I think I'm onto something with these Sumerian blood rituals, but that slowed me down because my translations weren't making sense, so I had to stop for a couple months and brush up on my Ancient Sumerian."

I found the reference I'd been seeking and returned to the other side of the table, opposite Marvolo. I thoughtlessly snatched a parchment out of his hand and turned it back so that I could read it, flattening it on the table while I compared my calculations with the charts in the book.

"You really think it might work?" he wondered.

I snorted quietly, "Well, we literally have the world's best resources at our fingertips, Marvolo." We'd finally compromised on Marvolo when I had refused to call him Voldemort and Marvolo had refused to not draw his wand at the first utterance of Tom. Really, it had just gotten old after the twelfth time we'd dueled the death over the man's ruddy name. "And we have pretty much forever to work on it. So… I figure that if it is possible, we'll get it eventually. And I stopped believing in impossibilities after the third time I died."

Marvolo nodded thoughtfully. "Want some help?"

"Yes," I smiled. "I was dreading another delay to improve my comprehension of Atlantean."

He smirked in return and ducked under the table to join me. I pointed him to the offending ancient book and he set to work on it.

2129 – 109 years

"You're really quitting?" I demanded furiously, hopping off the balcony after Marvolo. An almost thoughtless application of a wandless, silent flight spell slowed my descent comfortably.

"Harry, I have better things to do with my immortality than spend another decade chasing your wild goose. What you're looking for doesn't exist. Admit it and move on."

"Better things to do?!" I persisted incredulously. "Like what? We're the last two bloody sentient beings on this fucking planet!"

"So perhaps I shall devote myself to devising the means to find another planet," Marvolo called back carelessly before launching himself into a brief flight toward his own study – walking it took an annoyingly long time.

I stared after him for a long moment, then huffed in annoyance and leapt back toward my research. He'd be eating his words. Oh, yes, he most definitely would. Find another planet… Fucking tosser.

2142 – 122 years

"Harry?"

"Oh, speaking to me again, are you?"

"Obviously."

"Don't get cheeky with me, Marvolo. You've been ignoring my existence for a decade."

"That's not true," the former dark lord frowned.

"That shag up against the bookshelf five years ago doesn't count," I sneered, "though I was grudgingly impressed that you managed to avoid saying a single word the whole time."

Marvolo adopted an affronted air briefly before shrugging. "Whatever. Do you still want help?"

"I should say no and leave your annoying ass here when I get this figured out on my own," I grumbled.

"But you won't," he smirked in satisfaction. "Because you like my help."

"I've long since sorted my issues with Atlantean."

"Well, I suspected that that was a ruse all along," he shrugged. "I know that it's really my charming personality that you miss."

"You might want to look into that trouble you seem to be having with delusions."

He just lifted an eyebrow.

"Fine. Help. Familiarize yourself with that," I pointed at a book and turned my attention back to my calculations.

2155 – 135 years

"This is stupid. This is pointless. This is a waste of time."

"I think you've actually grown more immature with age, Marvolo."

"Shut up, brat."

"You are two hundred and twenty-eight years old and you're pouting."

The former dark lord literally stuck out his tongue.

I just shook my head. "You can't waste time when you have all the time in the world."

"I thought so too, until I was foolish enough to take up this gods' forsaken quest of yours."

"What are you bitching about now?"

"Time travel. It. Is. Not. Possible."

"That again? You realize that you bring this up every couple of years, right?"

"Evidently, that is how long my bouts of temporary insanity tend to last. I can't imagine why I've wasted this much time."

"Because you're just as fucking bored as me. Now either help or go pout elsewhere. I think I'm onto something here."

Marvolo snorted inelegantly and hopped over the balcony.

I shook my head and wondered briefly how long it would take him to get bored enough to come back. His interstellar travel idea was having even less luck than time travel. Interdimensional theory had also been proven "impossible". Granted, Marvolo declared time travel impossible every couple of years, but he kept coming back. This was our best chance at finding a purpose to our lives again, and even if it was so unlikely as to be nearly impossible, striving for that chance was better than nothing. Plus, though Marvolo would never admit it, he got lonely too.

2165 – 145 years

"Harry."

"Start over there."

"Have I mentioned that you're my favorite person in the world?"

"Now you're getting morbid."

2180 – 160 years

"Fucking OW, Harry!"

"Settle down. It'll grow back."

The red-eyed wizard sent me a glare meant to kill.

I ignored it and poked at the stub where his arm and sleeve now ended just below his shoulder. "I wonder what went wrong…"

"I hate you."

"Yes, yes. I know the Atlantean is right, so it must be in the Occitan…"

By the time I felt the killing curse coming at my back, it was too late to do anything other than die.

I woke with a gasp and a shiver. Fuck, I hated that. "You bastard!" I called at Tom's back as he jumped down to the library below.

"At least you've still got two arms, brat!"

"It'll grow back!" Honestly, he could be so touchy sometimes. It would only take a few days, less if he focused his magic into it. "Hey, Marvolo!" I raised my voice as I stood up. "It should be ready to test again within a month."

No response.

"Are you coming back?"

Nothing.

With a sigh, I turned my attention to the part that I thought was the problem. He'd be back eventually.

2194 – 174 years

"Morning."

"Where have you been?"

"Just walking around."

"For fourteen years?"

"Some of the time I was flying."

"Uh-huh."

"So…"

"Yep."

"Still working on it?"

"Getting close, too."

"You said that seventy years ago."

"Getting closer."

"Right."

"…"

"Need any help?"

"Done with your tantrum?"

"Yep."

"Sure."

2224 – 204 years

"I need a vacation."

"What? You're quitting again?"

"No. Taking a vacation. We've been working nonstop for three decades."

"That's not true."

"The trip to plunder Mesopotamian ruins was not a vacation, Harry."

"There was a beach."

"And we spent the entire six months in catacombs."

"But we found what we were looking for."

"You're disturbed."

"Not my fault. You're the one who hit me in the head with an AK when I was a baby."

"…"

"When are you coming back?"

"When I'm done touring the Pacific Islands."

"Right. See you in a few decades."

"Yep."

2234 – 214 years

"I wasn't expecting you back so soon," I noted when I heard Marvolo's entrance.

"Wasn't planning to be. Until I found the temple."

"Temple? You mean we missed one?"

"Mm-hm. Missed a whole civilization."

"What?" I finally looked up from my work.

Marvolo was smirking at me, clearly having predicted my response and enjoying that fact. "It predates Atlantis by more than a millennium."

"Why didn't we find any reference to it? Any sign of it?"

"To the second, it was built entirely underwater. To the first, the whole civilization cut itself off from the outside world five thousand years before Atlantis was founded. Amazingly potent preservation warding, really."

"Underwater? In some kind of bubbles, or something?"

"No, and that was interesting. Permanent human transfiguration. They made themselves into aquatic beings. I actually suspect that the merfolk descended from them."

I blinked. After all this time, I thought we'd gathered pretty much all there was to find about history. A new find after all this time was thrilling. Particularly one so potentially monumental.

"So. You up for a break?" he smirked knowingly.

I glanced around at the cluttered study filled with research I'd barely left in over a century. "Absolutely."

I ducked under the table and joined Marvolo in leaving the library through the oculus in the roof that was warded to keep the weather and birds out, but allow us free passage.

2300 – 280 years

"Gods, that's it. It's ready."

"Are you sure? Because the last time you said that, I ended up in three pieces. And I still don't know where my right leg went."

I sent him a glare. "I'm sure this time, okay?"

"Uh-huh. I'll believe that when I see another living human."

"Do you like eating your words?"

"In this case, it would make me ecstatic. Doubly so if I arrive in one piece."

"Mn. So you're ready then?"

"I still wish we could have found a way to make it work without human sacrifice."

"You complaining about human sacrifice. Now I've seen everything."

"Well, I wouldn't care if I wasn't being sacrificed."

I snickered at him. "There you are. Shiny new ritual dagger."

"This had better work."

"Your confidence is inspiring."

"Your previous attempts leave me justifiably wary."

"You act like you had nothing to do with engineering those attempts."

"It's always been your project, Harry. That means that you get credit."

"You mean blame."

"Yes."

I sighed. It concerned me sometimes, how obviously insane I might realize that I was when I again had average humans with whom to compare myself.

1967

I shivered violently as I woke. Death by blood loss tended to leave me with one hell of a chill. I rubbed my hands over my arms while I cast a quick warming charm, and looked around. Marvolo was just sitting up next to me, and carefully checking for the presence of all his body parts.

Well, we definitely weren't when we left. We'd used the ritual in the forest. We were now in a field, and I was pretty sure that was a village in the distance. With smoke coming from chimneys. I couldn't quite bring myself to believe it until I cast a tempus.

21 June 1967

12:34 p.m.

We'd gone back exactly three hundred and thirty-three years.

"Fuck. It actually worked."

"It disturbs me how surprised you sound."

I turned a brilliant grin on him. "We fucking did it!"

A smirked and nodded. "It seems that we did. And I appear to be all in one piece."

"Taste good?"

"Mn. Delicious."

For a long time, we just sat on the ground and stared at the distant village. And, then I turned the other way and temporarily forgot how to breathe. "Gods…"

Marvolo followed my gaze and I heard his breath catch as well.

"It's still here."

"Hogwarts."

"She's beautiful."

"Yes."

Another long moment of silence passed.

"What the hell should we do now?"

"Kill the muggles?"

I tilted my head thoughtfully. "All of them?"

"Can you think of a reason why not?"

"Muggleborns."

"So."

"So, what if we actually need them to sustain our population?"

Marvolo sighed. "Research?"

"Yep."

"You realize that we only have about thirty years before the war starts."

"Better get to work then."

"Where should we start?"

"Um. You can start grabbing and dissecting muggles. I'll search Ministry records for any research they've done on it," I suggested.

"Sounds good. Where do you want to meet?"

"Atlantis?"

"Well, we won't be disturbed there."

"Cool. See you in a few months."

"Right."

A/N: Please don't forget to review. I'll take one word or a thousand, at your discretion. ;-)

There may, at some point, be a sequel. Dunno.