Princess Luna looked at the Queen of the Changelings in confusion, "why did you-?"
"-let you get this far. Why it's simple really. I knew the Elements of Harmony are the only thing even possibly capable of defeating me. When I attempted to unlock the door with Celestia, she was rebuffed. Apparently the door can sense if you aren't in your right mind. So I needed you to do it, and to do it of your own free will. And now that the door is unlocked, I think that you'll all make fine additions to my kingdom."
Some of the changelings behind her changed shape into various people, some into the forms of the Bearers of the Elements of Harmony. The others simply elected to stay in their original forms.
Princess Luna leaned in close and whispered to the others, "we must use the Elements. Focus on freeing the other bearers; I shall distract as many of the enemy as possible."
As soon as she saw the others nod, Princess Luna reared up in the air, whinnying loudly. Then she charged, her horn flaring with magic.
Queen Chrysalis's forces (barring the Queen herself, Celestia, and Fluttershy) reciprocated. Rainbow Dash led the charge, still shouting in a ridiculous accent not at all befitting her, "coom on me lassies! Tis time to show this jack-a-mule who da real Queen oh Equestria is!"
XXX
It is often said that strength in numbers is one of the greatest advantages that one side can have.
It is also said that it is not a wise decision to charge straight at an Alicorn who is responding in kind.
To say that when the two charging sides met things went well for Princess Luna would be like saying that Pinkie Pie is a little energetic.
A more accurate metaphor would be to liken Princess Luna's onset as a bowling ball is to bowling pins when achieving a perfect strike.
And so strength in numbers, while still a good advantage to have, was completely wasted in this particular instance. This realization was visited upon many Changelings and two particular ponies as they each collided with the Alicorn of the Night and were each in turn knocked to the side against the walls, floor, and ceiling of the room.
All of them felt that they had learned a very important lesson (which some of them wondered distractedly whether they should mail Celestia with.) The lesson was very simple really:
"Don't charge Alicorns."
Once they all had had sufficient time to contemplate this nigh immutable fact of life (as well as manage to yank themselves out of the walls, floor, and ceiling) they felt that they had learned enough for the day and may as well get back to fighting.
And fight they did.
XXX
While Princess Luna's charge had indeed scattered everypony and everything in her path away like bowling pins, the reprieve was short lived. The Changelings recovered quickly and attacked. Most of them moved towards Luna cautiously. The remainder set their sights on the small group of ponies who were standing before the Elements of Harmony.
The Changelings smirked at what they thought would be an easy capture and moved aggressively towards the ponies. Pinkie Pie and Rainbow Dash followed the crowd and the other three who had remained in the doorway (Chrysalis, Celestia, and Fluttershy) moved into the room as well.
It was tense as neither side wanted to take the first aggressive move. Then the Changeling's patience finally gave out and they attacked. Luna struck out as the Changelings tried to bury her in an avalanche of their bodies. The rest of the Changelings charged the ponies situated around the box containing the Elements of Harmony. Princess Cadence's, Twilight's, and Rarity's horns flared as their magic zapped out, and Applejack stood in front of them. Her face was set in a death glare and any Changeling that came within striking distance of her hooves deeply regretted it. The three fillies huddled behind the small group, afraid of being devoured by Changelings.
Meanwhile Rainbow Dash was flitting through the air, urging the Changelings on to greater efforts and directing the flow of the battle. Pinkie Pie was also flitting about the floor seemingly at random.
The battle quickly degenerated into a brawl as the group of Ponies tried to defend their small area in the room and track their brainwashed companions, waiting for an opportunity to strike. Princess Luna was lashing out left and right with any and all weapons available to her including her hooves, her wings, her horn, and most devastatingly, her magic.
XXX
Fluttershy was huddling in a corner of the great hall, too afraid to actually do anything about the fight. Suddenly a flash of a teleportation spell occurred right beside her and Twilight Sparkle appeared. Fluttershy squeaked and tried to bolt but Twilight had anticipated her action. Twilight had entered the spell while jumping and she had left the spell while still in that jump. As a result, she landed directly on Fluttershy, effectively pinning her to the ground.
Fluttershy struggled but Twilight wasn't going to let her go. Before Fluttershy could do anything, or (lord forbid) deploy "the stare," Twilight touched her horn to Fluttershy's forehead. As she was doing this, Pinkie Pie popped up out of nowhere.
"Oooh, what're you doing Twilight? Are you going to make her all scary and mean because that's not very nice! Oh, or are you going to-" as Pinkie Pie continued on, the spell took full hold and Fluttershy's eyes cleared. She shook her head and then looked around as comprehension dawned in her eyes.
Then, appearing in a pillar of flame, Queen Chrysalis teleported right next to the trio.
"FOAL!" she shouted at Pinkie Pie "THEY ARE TRYING TO BREAK YOUR LOYALTY TO ME! ATTACK!"
Immediately, Pinkie Pie dropped low into a position resembling an angry dog and growled at the two ponies. She leapt at Fluttershy. Twilight was about to defend her friend when she noticed Queen Chrysalis's magic charging up. Twilight quickly threw a shield around herself as the Queen fired a hypnosis spell at her.
"Not this time Chrysalis," Twilight said. The Queen of the Changelings simply laughed.
Fluttershy meanwhile was hit by Pinkie Pie. Both ponies slid back and once they stopped moving, Fluttershy looked up into Pinkie's snarling face.
"Please Pinkie, just let Twilight help you. I'd really like it if you would stop being such a meanie-pie."
Pinkie Pie frowned, still not getting off. Then Fluttershy had an idea.
"Oh, don't you think that since Princess Cadence was the one who the wedding was for she would know where all the desserts are."
Instantly Pinkie's entire demeanor changed. Her face went form a frown to a gleeful smile and she hugged Fluttershy in a backbreaking grip.
"Oh oh, do you think she'd tell us where the Pie is?! I like Pie! But not as much as cake! Which is really weird since my name is Pinkie Pie! But anyways, I really like cake so we need to find some!"
Pinkie grabbed Fluttershy and sped off, somehow weaving in and out of the crowd of Changelings at speeds that would put Rainbow Dash to shame. Anything that got in her way was immediately knocked aside as she hunted for Princess Cadence in the mayhem. Spotting the Princess, Pinkie Pie sped towards the beleaguered Alicorn.
Cadence was indeed having a lot of trouble. She wasn't that good a fighter. Sure she'd had magical training and maybe she'd observed the guard a lot (well actually she'd mostly been paying attention to Shining Armor) but she really wasn't cut out for this sort of pitched battle. Now she was surrounded and alone. The Changelings were slightly apprehensive of approaching her because they knew just how painful an Alicorn's magic could get. But they were getting bolder, moving closer. Finally, their numbers giving them the necessary confidence, they all charged at once. Cadence hit as many as she could with her magic, but it wasn't nearly enough and the remainder crashed into her. More and more joined them as she struggled to escape the dogpile that was blanketing her. Just as the last bit of view she had of the room was cut off, something blasted straight into the pile of Changelings.
Somepony was kicking and hitting the Changelings off her at insane speeds. Cadence caught a flash of pink and yellow as she heard Pinkie screech, "I . . . WANT . . . MY . . . CAKE!" Each word was punctuated with her hind legs kicking several Changelings at a time.
As soon as the last Changeling was kicked off of Cadence, Pinkie zoomed up to her, her face alight with anticipation.
"So! Where's the cake! Fluttershy said you might know where the cake is! I really love cake! Even more than I love Pie! Which is really weird because DUH-" Pinkie finished as Cadence tapped a glowing horn to her forehead. Memories came surging back to Pinkie and the green glow in her eyes faded.
While she was processing the memories, Cadence and Fluttershy stood on either of her sides, warding off the Changelings (or rather, Cadence attacked the Changelings with her magic and Fluttershy stood trembling.)
When she'd finally finished remembering all her memories, Pinkie blinked, and then looked around. Fluttershy and Cadence waited with baited breath to see what she'd do. Then Pinkie Pie smiled while giggling, "I get it now. WRESTLING MATCH!"
With that shouted, Pinkie dived headfirst into the crowd of Changelings. Cadence and Fluttershy both cried aloud in surprise but then numerous growls and howls of pain coming from the crowd of Changelings reminded them that it might not be Pinkie Pie they should be pitying at the moment.
"Pinkie Pie!" Applejack called.
Pinkie looked up from where she currently had a Changeling, which had coincidentally taken the form of Applejack, on the floor frantically tapping the ground as if they were wrestling and it was trying to surrender.
"We need Rainbow Dash soes we can use the Elements of Harmony!" Applejack shouted to the Pink Pony.
"If'n anypony can catch Rainbow Dash, it'd be you Pinkie Pie," Applejack finished.
Pinkie Pie looked up to see Rainbow Dash flitting about through the air. Then she looked back at Applejack and nodded, smirking as she did.
XXX
Princess Celestia meanwhile judged that the battle had gone on long enough. She strode forward, her green-tinted eyes fixed on her sister as Luna wreaked devastation amongst the Changelings.
Princess Luna turned and saw her sister approaching. She frowned grimly, wondering if a confrontation between them had been inevitable. She quickly dealt with any Changelings still attacking her and then turned to her companions.
"Quickly, see to the elements Princess Cadenza!" Luna shouted as younger ponies gathered towards the small chest containing the Elements of Harmony. Luna turned and pawed the ground, snorting as her eyes narrowed.
"I have some business to see to with my sister."
Luna launched herself into the air and Celestia followed suit. Both sisters charged and met each other in a blast of power that knocked anyone close enough to them away. They locked horns, glaring at each other. Power ran along their horns as each tried to gain an advantage over the other.
The sheer amount of channeled power knocked them both back a short distance. Luna readied a sphere of darkness and quickly flung it at Celestia. It connected and expanded to black out her entire half of the room. The reprieve it gave was short lived however as beams of light blasted out of the darkness, starting to burn it away.
Luna wasted no time and charged. Celestia was not expecting it and Luna's attack connected dead on. The two Alicorns smashed against the far wall and Luna prepared to use the memory spell to free her sister. But Celestia would have none of that and fired another beam of light from her horn. Luna was hit and she spun away towards the floor.
She managed to right herself and impacted on her hooves. Her impact cracked the floor and she immediately looked up, wary of Celestia's attacks.
Meanwhile, Rainbow Dash was flitting about the room, urging the Changelings on to keep attacking the un-brainwashed ponies. Suddenly, she heard a shrill warcry and looked up. Pink filled her vision as Pinkie Pie dropped from the ceiling. She'd been hanging like a bat, waiting for the exact moment when Rainbow Dash would be directly below her. While there was no telling how she got up there in the first place, no one could deny that it was an effective tactic.
Rainbow Dash was hit and both Ponies fell to the ground. The Pegesus struggled and kicked but Pinkie Pie held fast and strong. Instantly Rarity, Applejack, and Fluttershy charged, carving a pathway through the horde of changelings (well, more that Applejack and Rarity carved the path while Fluttershy apologized to the Changelings for hurting them.)
During all this Queen Chrysalis was still going after Twilight. Twilight however was trying to play cat and mouse as she dodged Chrysalis's magical attacks. Twilight knew that she needed to get away from the Queen of the Changelings. She suddenly saw an opportunity and took it.
Queen Chrysalis had been momentarily distracted by the battle between the two Alicorns raging above her. When she turned back to attack Twilight, she found to her consternation that she was staring at a crowd of seven Twilights. She growled as she debated what to do. Then another blast of light from the aerial combat above successfully stole away her attention once again. This freed up Twilight to teleport right over to where her four other friends were attempting to hold down Rainbow Dash.
Both Luna and Celestia fired beams from their horns at the exact same time and their attacks met in the middle. Both sisters strained as their wills came into conflict.
But at that moment, the light of the moon came streaming in through the windows. Both sisters realized at the same moment that the reason for this was that the moon was finally setting; the night was coming to a close. Celestia willed the sun forth and for a moment, both the sun and the moon lay in the sky opposite each other. Then the moon sunk below the horizon. Celestia reveled in the newfound surge of power she felt as the dawn broke over the land.
Then the beam of light slowly began to overcome the one of darkness. Luna poured all she had into the attack, but only managed to hold on for awhile longer before Celestia's attack reached her and hit her in the head.
It hurt.
A lot.
Luna hit the floor and grunted in pain. She moved quickly, trying to get up before Celestia could capitalize on her weakness. She was a moment too slow as Celestia descended upon her, slamming her hooves onto her sisters chest and wings. Luna's breath whooshed out of her as her sister's hooves hammered her. Celestia then grabbed her sister in a telekinetic grip and flung her into the wall headfirst. Before Luna could recover she was grabbed again and was turned upside down so that Celestia could send her face first into the floor.
Celestia continued to fling her sister about the room, not giving her a second of peace. Luna tried to concentrate enough to break her sister's telekinetic grip on her, but the beating she was taking prevented it. Finally, after flinging her against the walls and floor, and blasting her with various concentrated beams of power, Celestia brought her sister right in front of her.
Luna was struggling to breath, various small wounds littered her body, shards of glass had left cuts in her flesh and she was unsure if one of her wings was broken. She was almost certain that several of her ribs were though.
Celestia studied her sister, internally debating what to do with her. She could of course attempt to brainwash her, but something told her that it would be time consuming now that Luna knew exactly what to look for and what to resist. It might even be impossible.
Keeping her prisoner for an extended period of time would also present its own score of difficulties, not the least of which being just how hard it would be. Luna was an Alicorn and thus was naturally skilled and naturally excelled in most every area that made ponies powerful. Sooner or later, Luna might find some way to corrupt their loyalty to Queen Chrysalis.
The answer was simple. But some part of Celestia rebelled against it; some part of her didn't want to do it. After all, wasn't Luna still her sister? Didn't she owe it to her to try and inform her of the Queen's great mercy, of how she would fix the world?
Celestia debated, and then made her decision.
XXX
Princess Luna cried in pain as a beam of power shot from Celestia's horn, hitting her square in the chest. Celestia continued the beam, not ceasing even as her sister looked at her with pleading eyes. Luna's eyes bore into her and Celestia finally closed her own eyes as she focused on maintaining her loyalty in order to see the execution through, it was all for the greater good. Luna felt about ready to pass out as the burning beam continued to hit her, charring her flesh as it seemed to eat away at her.
Then both of them heard a loud voice crying out, "STOP!"
All eyes turned towards the voice and they beheld Twilight, standing with her friends by her side, each wearing a respective element of Harmony. The Changelings all, knowing what this meant, charged without plan or hesitation at them, hoping against hope to overbear them before they could utilize the most powerful of all known magics.
But for them it was too late. The Elements began to glow, and any Changeling that touched them was flung back as if it had been dealt a heavy blow. A bubble made of rainbows expanded from around the six ponies and blasted outwards faster than anypony could tell.
Any and all Changelings caught in its wake were sent flying in all directions away from Canterlot. No minion of the Queen, or even the Queen herself was spared as they were thrown through the sky, disappearing into far distant lands. Whether they would even be able to find each other and gather again couldn't be guessed.
But as for all the ponies caught up in the power that was unleashed from the Elements, their minds were cleared. The glow of green in their eyes died and everypony stumbled around as if in a daze for a few moments. Then realization struck them as they realized what had happened, and some wept, others were relieved that the disaster had passed, and still others reacted angrily, berating themselves for not resisting the spell they had been under.
But nopony felt these things more thouroughly and more grievously than Princess Celestia. As she was put back into her right mind, her eyes first landed on her faithful student Twilight Sparkle, and she remembered how she had driven both her and Princess Cadence back into the Crystal Mines and had several times nearly gotten them captured. Then she looked around at the room, recalling how she had so easily handed over complete control of Canterlot to Queen Chrysalis.
And finally her gaze turned to her sister and her eyes glistened with tears. Luna was lying on the ground, panting and nearly unconscious. Though the Elements had healed her wounds, the experience she had gone through still had taken a great toll on her body and mind. Celestia moved towards her sister, intending to apologize, but the words caught in her throat and to her, any apology seemed woefully inadequate.
Then Luna's head fell back as she finally succumbed to unconsciousness.