Twilight stood there, in the great throne room of the Canterlot royal palace, fuming at the sight before her. Her brother, Shining Armor, standing triumphantly in front of her, the beloved crown of their youth resting atop his head. Her mind raced with the injustice of that sight, and her expression was one of utter annoyance, even as her brother placed the crown upon one of the two thrones. He walked down, and kept on talking about all the beefed-up security he'd been putting around, and of course taking great delight in just how smug he was being right now. Twilight knew, in his mind, he'd already won. He'd thought of everything, every plan she might come up with, all to ensure he would be the one to walk away as the Sibling Supreme forever. She would not stand for it. Not this. Not the challenge that had plagued her since her earliest years. She would emerge the victor, no matter what traps and schemes her brother had created. And as he finally approached her, looking more confident than she'd ever seen him, she was sure to let him know.
"I promise you, brother...I will be the one walking away with that crown."
Shining chuckled.
"Oh, Twily. Twily, Twily, Twily. You've accomplished a lot in your time, but you're taking to a master of security here. I've been involved in things like this since you were still a filly. Make no mistake..."
He leaned forward, giving her a pat on the head, as befitted an older brother.
"...the only thing you're going to be walking away with here is a slice of humble pie."
Twilight, though still fuming inside, smiled. It was a dangerous smile though, one that made clear that she wasn't one to be trifled with. What's more, it was a smile Spike could feel a great deal of danger from, like the bared teeth of a vicious predator. Shining too smirked, and the brother and sister pair stood mere inches away from one another. They loved one another, and they'd do anything for one another, but this was a childhood title they were taking about, and there were few things in this world that can cause a conflict between families like that.
"Hmmm...it would appear that your resolve to emerge as victors is equal, and impressive to behold."
The sudden arrival of this new voice caught both of them off-guard, and for the first time since this meeting began, the siblings turned, focusing on something other than each other. As they turned, they found that it was none other than Princess Luna who had spoken. The younger of the two alicorn sisters, stepping ahead of Celestia, now had everyone's attention, and as she regarded the two, she smiled, but in a way that implied a great deal of thoughtfulness.
"Truly, this conflict harkens back to the days of yore, when great minds and forces of will would clash over matters of honour and glory. Truly, we are witnessing such a test this day."
Celestia, who knew her sister better than any pony living, could immediately see where this was going, and gave herself a facehoof.
"Oh...no."
Luna, unconcerned with her sister's exasperation, continued, looking to the two younger ponies intently.
"Twilight Sparkle...Shining Armor...it is clear to me now that the importance of this crown of your family is not one that can be settle through a mere, as you say, heist."
Shining's eyes widened.
"Wait, what?!"
Luna nodded.
"Indeed, Sir Shining. For this obstacle course you forged is an unworthy decider for the glory of victory. Hence..."
A smile formed on her lips.
"...I believe a better test should be devised."
Shining was aghast, and fumbled his words.
"But...but...but...I spent weeks working on all this!"
Luna nodded, placing her hoof upon his shoulder.
"Indeed, and we are truly grateful for the expertise you gave to our security. Truly, it would be impossible for us to feel anything but safe here."
She smiled.
"You have our thanks."
But then, her visage became sterner.
"As for the crown, there is only one contest that can truly determine its owner!"
Her horn flashed, and all there knew that something big was about to happen. Before anything, Twilight glanced to Celestia, who in turn merely sighed to her former apprentice.
"I am so...so sorry."
Then, the flash happened, temporarily blinding all there. Twilight could feel it, and recognised it instantly as a teleportation spell of some kind. Eventually, the light faded, and when her eyes finally adjusted, Twilight looked on with shock at their new location. It was a place she'd never scene, an arena, a coliseum, vast in scale, where the seats were already packed with row upon row of cheering ponies. Shining was close by, and he too seemed taken aback by this, looking around with utter confusion. High above, in a royal box overlooking this arena, were Luna and Celestia, with Spike close beside them. Soon, the Princess of the Moon stepped forward, using a spell to project her voice outwards.
"Mares and stallions of Equestria! We are gathered here today to witness a clash of titans! A war between a great and noble house!"
Twilight blinked.
"Ooooooookay, I see where this is going."
Luna continued.
"Twilight Sparkle! Princess of Friendship! Many-times saviour of Equestria! And perhaps the greatest mage of her generation!"
The crown roared with approval, and Twilight, albeit nervously, gave a wave back to them. Luna, looking to her opponent, spoke aloud again.
"Shining Armor. Renowned former Captain of the Canterlot royal guard! Prince and defender of the Crystal Empire! Bravest and most stalwart of stallions!"
Another cheer, and Shining followed his sister's example of not being quite as confident in his return wave. Twilight, scouring the area, noticed, to her surprise, that her friends were all here, among the crowd, waving to her and cheering her on. Though confused as to exactly how they got here or why there were so relaxed about this measure, Twilight still waved back to them, then glanced up to Luna as the latter gave one final command.
"For the honour of the title of 'sibling supreme'...let battle commence!"
The cheer from the crowd was near-deafening, as pony after pony called for battle and blood. Twilight and Shining, though bewildered, looked to one another. Brother and sister, lifelong friends, allies more times than they could count, now in the ring of battle against one another. Sighing, Twilight spread out her wings, her eyes narrowing towards her beloved brother.
"Well...I guess we always knew it would come to this, Shiny."
Shining hung his head, shame coming to him.
"I...I never expected that our quest to be named best sibling would lead us to this..."
After a time of having his eyes closed, he opened them again, looking to his sister with fire.
"...but I suppose...it was inevitable."
His horn ignited, and he pointed it down to his sister.
"Ready yourself, Twily. I have had experience in battle since before you ever even stepped out of Canterlot!"
Twilight smirked, matching his pose.
"Oh yeah? Well you're looking at a mare who's fought some of the worst creatures this world has to offer! Don't underestimate me, BBBFF!"
Their horns glowing ever brighter, they lunged forward, screaming at the top of their lungs, before colliding in the centre. The flash of the impact, and the strength of their magic, was immense, and it sent shockwaves across the entire arena, causing many an onlooker to be forced back, some even sent flying off entirely, though screaming with satisfaction as they did so. Twilight's friends cheered louder and harder than any pony there, waving their custom "Go Twilight" flags with great vigour. When the initial clash died down, Twilight and Shining were forced back, their hooves digging hard into the ground below. Though surprised at just how intense that had been, they charged again, upping their power, and causing yet another shockwave with their second collision. The crown loved it, and as all looked on at the family fight below, Celestia, who was actually looking rather embarrassed at all this, glanced to her sister.
"Luna, sweetheart? I don't mean to question your tastes, but are you certain this is a good way for the two of them to resolve this conflict?"
Luna glanced back to her, frowning.
"Sister, you and I know the ancient law. Matters of honour and dignity, when the stakes are this high, and the bond is this deep, can only be settled by courage and combat. It is the ancient way, and so it shall be here as well!"
Celestia raised an eyebrow.
"Right...and the fact that this give you an opportunity to see a younger sibling give an almighty beat-down to an older sibling is just a coincidence?"
Luna paused, tapping her chin and giving a quick shrug, trying to look and sound as innocent as she could.
"Oh, I suppose I do get to see that. Who would've thought?" she replied, hiding her smirk as she turned away from Celestia.
Down below, the fight was getting intense, as spell and counter-spell and counter-counter-spell had been thrown one way or the other, leaving the battleground as little more than a charred and wrecked mess right now. Twilight and Shining, though still prepared to carry on the fight, were nevertheless panting furiously.
"You...you...you're doing pretty good, brother," Twilight remarked.
Chuckling, albeit in a tired-sounding way, Shining smiled back to her.
"You're...not so bad...yourself...Twily."
Twilight laughed back.
"I see...life in the Empire...hasn't made you soft."
"And I see having a life of preaching peace and friendship hasn't dulled you either," Shining replied.
The two shared another laugh together, giving them a nice, if strained, moment of calm in this fight. During this wistful bonding time, Twilight began to wax nostalgically.
"Reminds me of the time we had to compete with our own hoof-written poetry to win the crown that one time."
Here, Shining's smile faded, and he scowled at her.
"I was the better poet that day and you know it!"
Twilight scowled right back.
"Hey! Mom and Dad said I was better! End of discussion!"
With renewed vigour, the two lit up their horns again, gathering their admittedly diminished strength to resume their fight, with years-old grudges now drudged up to fuel their fire. Their battle cries echoed throughout, even superseding the calls for violence among the crowd. And speaking of the crowd, it appeared as though it received four new onlookers. Princess Cadance, Flurry, and Twilight and Shining's parents had all just arrived, and were, in fact, seated next to Celestia and Luna in the royal box.
"So...what's this about?" Cadance asked.
Giggling, Twilight Velvet leaned next to her, giving Flurry a quick pat on her head as she did so.
"Well, it all began when they were children, and they've had this little contest to get this silver crown through things like good behaviour and grades and such."
Cadance arched an eyebrow, pointing to the arena.
"And blood sports, it would seem."
Night Light scratched his head.
"Hmmm, yes, that is somewhat more intense than they usually go."
Cadance, looking more than a little worried, looked down to her daughter.
"I'm not sure if this is the best place for me to bring Flurry. Who knows how upsetting this will be for her to see her Father and Aunt do battle like this?"
But Flurry, contrary to how her Mother might have expected, instead just appeared to be having the time of her life, mimicking the motions of all the fight moves she was witnessing down there.
"Ba! Baboo! Babooobaboo!" she gurgled, imitating a particularly vicious series of punches.
Cadance, seeing that, sighed.
"Yep, definitely going to have coliseums built in the Empire when she comes to power."
The fight below had become an utterly devastating affair, with the ground little more than a blasted and fiery hellscape. Oh, what horrors had been unleashed in this duel of honour? It was truly beyond the ability of the onlookers to grasp. But as the fighting drew to its inevitable climax, Shining at last found himself on the losing side of this conflict. His magic drained, his body weak, he could no longer even stand upright, instead having been reduced to a crawl. But soon, he crawled right to the hooves of his sister, whom he now looked up to.
"Twily...I...I'm not giving up."
Twilight, though battered herself, still had some fight in her. More than her brother certainly. Though as she looked to him, she smiled, reaching out her hoof.
"Shiny...my BBBFF...I offer mercy. We can be friends again."
Shining looked to her, eyes full of hope, only to then have that hope snatched away when she next spoke.
"Aaaaaaand all you have to do is admit you've lost and that I'm 'sibling supreme' forever."
The fallen stallion frowned, his voice full of defiance.
"No...never!"
Twilight's smile vanished, replaced instead with grim acceptance of the situation. Her brother would not yield the crown, and all in attendance knew how this was going to play out. In the crowd, her friends watched, right on the edge of their seats, at the final victory that was about to be unleashed.
"Well, Shining put up a valiant fight...but he was doomed before he started," Rarity remarked.
"Yeah...what a waste of bits to bet on that guy," Rainbow answered.
The other mares looked to her, leading to a quick back-pedal on her part.
"Oh! Er, I mean...go Twilight?"
And speaking of Twilight, she sighed deeply, knowing that there was only one way this fight could now end.
"So...that's how it is."
Her eyes opened, though narrowed, to her brother.
"This is the end, brother."
She raised her hoof, ready to bring it down and finally end this conflict. Shining winced, shutting his eyes tightly, and the crowd all watched with bated breath to see this final blow. Then, the hoof came down. But it was not a deadly strike nor vicious attack, but rather a simple tap on his head.
"Tag...I win."
Shining, contrary to his previously-exhausted look, leapt to his hooves, looking utterly dejected.
"Ugh! No faaaaaaaaaair!"
Twilight, now smiling again, simply shrugged.
"Hey, a tag is a tag, Shiny. I win the crown."
Shining slumped onto his rump, folding his hooves and pouting.
"I should've won!"
Twilight chuckled, moving forward and giving him a hug.
"Sure you should've, brother. Sure you should've."
The crowd, naturally, were a bit perplexed at this, and so looked up to Luna, who glanced down to them with confusion.
"...What? You didn't think I was going to have them kill each other over this, did you?"
Taking more than her fair share of amusement in the way all those onlookers were coming to terms with this revelation, Luna turned, clearly satisfied with this.
"Well, that was fun."
But, her cheery demeanour only lasted for as long as it took for her to realise that the crown, the great prize that this fight had been made over, was no longer on the pedestal she'd put it on.
"...Sister? Where's the crown?"
Celestia, who had been utterly disinterested in this for some time now, regarded the pedestal herself, then gave a shrug.
"Oh, that? Spike swiped it at the start of the fight and then ran off cackling. He's probably all the way back in Ponyville with it now."
Luna winced, looking back over her shoulder.
"So...any volunteers to tell those two down there?"
"NOT IT!!! all the others called out at the same time.
Luna, having missed her chance, grumbled.
"Oh, this ain't gonna be pretty."
Author's Note
So, two hundred episodes. Happy to see MLP make this great milestone, and of course, I just knew I had to make a fic for it. But I tell you, actually thinking of something for it was no easy thing. I went through several scenarios, but none of them seemed good enough, since the episode itself already ticked off all of my personal boxes.
Then I thought, meh, let's just have some off-the-walls nonsense with a fight to the (almost) death 
