AN: The first thing that came to mind when I saw Youjo Senki was how, timeline-wise, it was pretty compatible with Amestris. Played around with the idea for a while, and decided to just give it a shot.

Disclaimer: Youjo Senki is owned by... actually, I don't know who owns it. But it probably won't matter, because the Empire will take over and nationalize the company.

THE SAGA OF TANYA THE ALCHEMIST

A Youjo Senki x Fullmetal Alchemist Crossover

By Fizzy 13

Prologue: Deus X Machina

Being X took a sip from a glass of holy water, resting his elbow on the counter of a bar floating in the middle of some starry night void. "So what have you been up to lately?" he asked the featureless white entity sitting on the bar stool next to him. It had been a while since they last talked, what with the hard work of running a world with 7 billion people on it. Even gods needed a break every now and then.

"Oh, you know, this and that." The Truth shrugged as it drank from a featureless white glass that seemed to mimic the appearance of Being X's glass of holy water. "Last week, this pompous dwarf in a flask tried to eat me."

"… what?" Being X blinked. And here he thought his current problem was a headache.

"My world has some pretty interesting rules governing it, you know. Keeps things exciting." The Truth chuckled as it took another sip. "Of course, whether it's an artificial lifeform made by alchemy, or some naive kids who want their mommy back, nobody messes with the Truth and gets away with it."

"Hah, your confidence is as refreshing as ever, my friend." Being X sipped from his cup, empting it. At the waving of his hand, the barkeep walked over and refilled his glass.

"You don't sound too happy yourself," the Truth observed. After all, it was the Truth. It had to be honest. While there was nothing wrong with a little bit of understatement, it never went to the point of being excessive. "What's eating you?"

Being X sighed. "Well, I just ran into this unbeliever who got hit by a train."

"So?" The Truth shrugged. It didn't seem so serious. Last it checked, Being X's world had gotten pretty secular. "I mean, don't you just send those down to the bad place?"

"I don't have a bad place," Being X explained, somewhat annoyed. "I mean, I'm not that guy, you know. My world runs on a Law of Cycles."

The Truth snickered. "Madoka? Is that you? I'm sorry, I couldn't tell from the big white beard and all."

"Oh, ha-ha," Being X rolled his eyes, even more annoyed now. "I didn't mean that particular Law of Cycles. I was talking about a Cycle of Reincarnation."

"Well duh, I knew that." The Truth brushed off the correction and bottoms-upped its glass. "Speaking which, I haven't seen that girl in a while, either. It's too bad. She's really sweet."

"Last I heard, she was busy attending to some personal business in her world." Being X sighed. How did this get so off-topic? "Anyway, back to my problem. Like I said, I ran into this unbeliever whose number had come up. But he had the gall to question me!"

"Hey, at least he didn't try to eat you."

"Why would an unbeliever try to eat something he doesn't believe in?" Obviously, this dwarf in a flask believed in the Truth, otherwise, it wouldn't have gone through the hard work of trying to eat It.

"Seems like I pay more attention to your own world than you do," The Truth said as it asked for the barkeep to fill up its glass. Briefly, as the holy water went into the glass, the featureless white being took the shape of an outline matching the barkeeper's appearance. "A lot of your unbelievers are pretty vocal about it, you know? They don't just unbelieve in your existence. They loathe the very idea of it, and spread this loathing to anyone who'll pay attention. In case you haven't noticed."

Being X waited in silence. He didn't need to be lectured about how unbelief was spreading across his world. "Are you finished?"

"Yeah, go ahead."

"So I decided to perform an experiment on him."

"Yeah?"

"See, my pet theory is that humans lose faith in us when their scientific understanding and living standards increase. It's a testament to their arrogance." Being X stopped to take a sip from his glass. "The more they know about the workings of the universe, the more likely they are to think that they are the masters of it. For example, for thousands of years, only birds could fly. Then, starting a little over a hundred years ago, anyone with enough money could just buy a ticket and get on a machine that flies faster than any bird. Today, people don't think twice about flying, and how much time I spent planning out the evolution of wings."

"Aaand?"

"So, I decided to test this theory out. I will reincarnate him with his full memories, into a world of lesser creature comforts, of pain and suffering. And through his suffering, he will know me."

If the Truth had visible eyes, Being X would have seen it blink a few times in between giving him a blank stare. In this case, it was quite literally, a blank, faceless stare.

"What?"

"Honestly? I think your plan is dumb. He'll just hate you more. Humans tend to hold grudges, you know?" The Truth rolled the ice around in its glass before taking a sip. "I mean, why don't you just give him a clean start, and see if it happens?"

"Because, the point is to show that in a world with lesser creature comforts and lots of suffering, when they rely on us, then their faith will grow."

"So… you want to put an atheist in a foxhole." The Truth began to shake its head.

"There are no atheists in foxholes," Being X waved his finger as he took another sip.

The Truth sighed. "Well, where exactly are you going to put him? Africa?"

"What? No, of course not!" Being X put a hand to his chin, rubbing his beard. "Actually, that's the problem. I don't know where this guy should go. I mean, I could probably make a new world just to teach him that lesson…"

"Sounds like a lot of hard work," The Truth said. "Aren't you already overworked from managing your Cycle of Reincarnation?"

"Uh…"

"Tell you what," the Truth held its hands in an open palm gesture. "Why don't you put him in my world? It might look pretty stable, but there's a lot of instabilities going on in there, politically speaking. Push a few buttons in the right places, and you – that's right, I'm also letting you play around in there – could very well cause a world war."

"What's the catch?" Being X was familiar with the Truth. It operated the Law of Equivalent Exchange. To obtain, something of equal value must be lost. That was how it governed its alchemic sciences. And it treated deities the same as mortals. "Equivalent Exchange, remember?"

"Right, well, I was thinking, maybe you could, I dunno, take over my job while you're running your experiment? Because after almost getting eaten by that dwarf, I think I need to take some time off."

"But who's going to run my world?" It was tiring enough to run one world, let alone two. So the implication, of course, was that Being X would devote himself entirely to running the Truth's world while the latter took its well-needed vacation.

"I dunno." The Truth shrugged. "Maybe you can let that extremely sarcastic high school kid who only ever goes by his nickname take charge of it. You know, the one who babysits their god?"

"You mean John Smith?"

"Yeah, I think that's another name they call him." The Truth finished its drink and held out a hand for a shake. "So, do we have an exchange, or what? I mean, you don't have to start now, if you don't want to. Go find someone else to run your world first."

Being X hummed as he mulled over this proposition. It was certainly less taxing than making a whole new world, and the worst he had to do in terms of preparation was read up on how the laws of alchemy worked. If anything, it was a complete no-brainer. Nodding to himself, the deity took the Truth's outstretched hand and firmly shook it. "It's a deal."

The Truth smiled. It was a gargantuan, cartoony grin, displaying a perfect row of teeth. Yet even without the rest of a face, or perhaps, because there was nothing but a mouth on its head, it would seem to some mortals as creepy or disturbing.

Being X didn't mind. He'd spoken to stranger people before. Cthulhu, for example.

"Excellent!" A featureless white outline of a fishing hat appeared on the top of the Truth's head, and it hopped off the stool, waving goodbye as it turned away to leave. "Well then, I guess I'll let you have fun with your experiment! Me, I'm off to have a different kind of fun! Cheers!"

Being X took the time to enjoy his drink. There was a lot of work to be done, but if he got things just right, he could have possibly been looking at a new believer…

AN: Yes, I threw in a few other references there. Because silliness, or something. No Tanya yet, but I figured I'd set a precedent before anything else.