Luna was peering with intense focus at the bagel she was buttering, but she gave a lazy roll of her eyes as she spoke;
"...I'm just saying, their first album was much better than their second—"
"Luna! Don't even finish that!" Celestia barked. "Do you wish to start a civil war?"
Cadance had been detached from the sister's bickering, idly flipping through a magazine, but she set it down wearing a mischievous smirk. "Y'know, we keep saying that, and I know you mean it jokingly, but it really begs an obvious question: in an impossible hypothetical scenario, where the three of us went at each other gloves off, who would win?"
"Huh," Celestia said. "Interesting question. What are the stakes? What are we each fighting for?"
"Aw come on, Auntie! The idea of us fighting is absurd enough, don't complicate it with intelligence! It doesn't survive past that. The point is the fight. Just pretend we all want Equestria for ourselves and we're not willing to stop for anything. Who comes out victorious?"
"Well, what are the conditions?" Luna posed.
"The three of us, right now, as is," Cadance elaborated. "No Elements of Harmony, no Nightmare Moon. Just our own magic."
"Huh," Celestia said, already beginning to blush. "I mean, to be frank, I can admit that as a mare who has actively sought a pacifistic solution for more than a thousand years, I am a poor fighter."
"Mhm," Luna nodded. "Plus, you're a wise and motherly mentor figure to a powerful but undisciplined young pony. Mares like you are usually axed off in the second act."
Celestia looked a little taken-aback. "Uh... that's oddly specific, but sure. So in a show of pure power against you two without the luxury of planning or intelligence, I would probably be the first to kick it."
"To be fair," Cadance offered. "It would probably be from doing something cool like saving Twilight and her friends or something. Your last words would be all 'don't blame my sister' or 'don't blame my niece,' and it would be epic."
"Aw. You flatter me. While theoretically killing me," Celestia said. "Oh! Also, I would leave behind a sun nopony could raise, and then you'd all freeze. So really, I would win in the long run."
"Hey! That doesn't count!" Luna protested. "We already agreed that we weren't going to think about any before or afters. This is about the fight. And you're out. Which makes me the victor! Theoretical Equestria is mine! Or rather, Theoretical Equestria is Theoretical Luna's."
"Wait, hold on a second!" Cadance protested. "Theoretical Cadance would still be in!"
"Oh, right..." Luna chortled rudely. "The Regent of the Moon and Mistress of Dreams, versus her adorable lovey-dovey niece."
"Exactly. I win."
"Right, right," Luna was grinning ear to ear. "With your ever-so-terrifying love magic, I presume?"
"You're damn right," Cadance said, wearing a smile somewhere between humorous and terrifying. "You've got the moon and your dreams, so yeah, maybe I'd have to start popping caffeine pills so you don't trap me in a nightmare or whatever, but all I'd need to land is one magic shot and I could have you try to make love with the inside of a volcano or something."
"Wait..." Luna blinked. Her grin fell. "Your love magic..."
"Yeah." Cadance intensified her smile. "I mean, I only ever use it on ponies who I feel already have a bond. I'm not a monster and I really don't want to have to worry about my conscience keeping me up at night on top of Flurry already doing that. But theoretically? Every mind in Equestria is mine, if I want it to be. And you wanna know how I know, Luna?"
Luna seemed too stunned to answer, but Cadance proceeded anyways.
"I know, because right now, you're drinking my caffè corretto with a stupid grin on your face."
Luna blinked, looked to the unholy beverage in her grasp, and all colour seemed to leave her. The cup began to spasm in her magic and by the time she set it down on its saucer the diner table was a mess of caramel, whipped cream, and not-coffee.
Celestia herself had noticed Cadance's horn aglow for some time, and was trying and failing to repress light giggles.
"And on this day," Celestia said. "We received a grim reminder; our own dear niece has the potential to be the most terrifying foe in Equestria. I don't believe it is a coincidence that Chrysalis chose you to impersonate. You're the closest thing to a mind-altering bug queen we've got, she must've felt quite at home."
"I don't know whether to be insulted or honored." Cadance rolled her eyes.
"Honored," Luna finally spoke. "Definitely honored. As a mare who failed miserably at her throne coup, some twisted part of me is forced to admire those who came closer than I did."
"I mean, let's be completely honest," Celestia mused. "We all would make pretty good villains if we wanted."
"Well, if me and Luna were evil and teamed up, the daytime would probably have to go, Aunt Celly. Sorry."
"Wait, what?" Luna perked up. "Why?"
Cadance facehoofed. "Eternal night? Insane love goddess? You seriously don't see the correlation there?"
"Could you please stop there?" Celestia groaned. "I'm not a prude or anything, but it's a little awkward hearing the mare I practically raised from birth talk about her theoretical empire of debauchery."
"Fine. But don't forget, I'm the mare who had a nuclear winter living in her womb. Thereotical Equestria would be mine," Cadance said, channeling a mocking Chrysalis. "In which case, your last words wouldn't be 'don't blame my niece.' They'd be 'I royally screwed up giving that mare wings and magic."'
Silence for several seconds. Celestia was the first to break it.
"Cadance, I don't believe I've ever been as proud of you as I am right now."
"Aw. Thanks, Auntie."