Chapter 4: Family Reunion
The next thing Twilight knew, they were in Canterlot Castle, inside the Princess's bedchamber. The windows had thick, magical bars blocking them, and the door had been magically sealed. It was clear the Princess had previously barricaded herself in to keep herself safe from the corruption.
There was a maid inside the bedchamber, keeping herself wrapped in a heavy cloak---that made Twilight notice that it wasn't much warmer in the bedchamber than it had been in the weather factory. It was hard for Twilight to tell at first that it was so cold; she was still bundled up under a raincoat and a sweater, but then she realized she could see her own breath.
The maid bowed and sheepishly said, "I apologize, milady, but the supply of coal is gone! When it began to get cold and you told me to stay in here, I lit a fire, but I didn't know whether or when you would be back, and...before I knew it, I---"
"It's all right, Sundancer," Celestia assured her. "Has anything happened since I left?"
"No, milady," the maid answered. "Some of the pegasus royal guards tried to break in through the window, but the bars held. They stopped trying and left when I got out of their sight. Beyond that, there hasn't been a whisper."
"Good. I'm going to send out a detection spell and wait here for the spell to return."
"Is there anything I can do for you, milady?"
"Yes: fetch us some towels. Twilight and her friends got soaked in Cloudsdale."
"Right away, Milady!"
As Sundancer scurried off to another room to get towels, Celestia knelt down and looked Twilight in the eyes---she was scanning Twilight, but what she was looking for, Twilight didn't know. But what Twilight did know was that something was troubling Celestia.
"What's wrong, Princess?" Twilight asked.
"I've...run out of tears, Twilight," Celestia softly answered.
"Me, too," Twilight admitted.
"I'm sorry, Twilight---I knew how much my approval means to you, and I still---!!" Celestia stopped talking and just looked at the floor sadly.
Twilight couldn't think what to say, so she just snuggled next to the Princess---she must be the cold one, now! It was a cold, cold night, and she had no cloak! She slowly spread her wing over Twilight, and they again just stared into each others' eyes. Twilight could see nothing but sorrow, guilt, and love in her mentor's eyes, and but she could only wonder what Celestia saw in hers. Probably concern, maybe fatigue---she'd been fighting all day, and...well, she still did feel more than a little shocked from their adventure in Cloudsdale. Twilight had hardly thought about what she was feeling, anymore---she'd been so concerned about what the Princess was feeling; her terror, her suffering, her guilt---her rage. Twilight hadn't thought about her own feelings since the forest.
And she shouldn't think about them now: she should think about the Princess. She'd been through so much; was the Princess getting too tired to go on? Did they need a rest? Twilight had needed a rest back in Everfree Forest---but then, the Princess could get her rest in spirit form, too, so maybe they could keep fighting, even while---
"Twilight, how are you feeling?" the Princess asked.
"I...I'm a little tired, but I can keep going," Twilight answered.
"...That's how your body feels. But how do you feel?"
Twilight remembered that those were the same words she'd used on Pinkie not long ago. She answered, "I...I'm still a little shell-shocked, I guess...I'm really, really glad you're not going anywhere. But...most of all, I feel worried about you, right now."
"I'm mostly worried about you too, Twilight. I've put you through far more than I should have. First I scream at you, and then I say I'm going to leave you forever...even when I know how much our relationship means to you."
Sundancer saw that this was a precious moment, so she set the towels down on the bed and slipped back out of sight. Celestia picked a towel up with her magic and began wiping the rainwater off of Twilight's slicker, before drying herself off from all the snuggling she'd been doing with her drenched student.
"I can see that you're very weary at heart," Celestia continued, "And...it's my fault you are. I'm sorry for doing this to you, Twilight."
"I forgive you for that, too, Princess," Twilight said without hesitation. "Please...is...is there a way we can all just stop being so sad?"
Pinkie interrupted, "She's right! I keep saying it, but nopony listens to me: why do we have to be sad!?? We all care about each other, we're all here---what's there to be sad about?!"
Celestia was silent, staring at Pinkie's orb for a moment, then she chuckled lightly. "You're right, Pinkie; you're right." She gave Twilight a happy nuzzle.
For a moment, Twilight saw the simple, merciful wisdom in what Pinkie was saying, and she recalled how she admired and loved that soothing, simple wisdom her friends had shown her back in Everfree forest---but then Twilight suddenly remembered another, terrifying thought that had occurred to her in the forest---one she'd not really gotten away from: the fear that the emotional roller-coaster wouldn't stop. Immediately after her friends had assured her that her doubts were unneeded (and, in some cases, silly), they'd had to brave the torrential storms of Cloudsdale---and far, far worse than that, she'd almost lost her beloved Princess! Just when she thought things couldn't get any worse, they did. And they now had a little time to catch their breaths, so it was just about time for things to get worse---probably far worse than Twilight could now imagine!
"Twilight, didn't you hear what I just said??!" Pinkie asked grouchily. Apparently, Twilight's face had given away that she was thinking about something that was both horrifying and saddening.
She decided to try to put what she was feeling into words again. "Every time something good happens to us...something else that's awful happens right afterwards! We finally feel better after resting up in the forest, and Ponyville's under attack, and then the storm comes, and the Princess is scared, and...and---!! You remember what I said in the forest about how the emotional roller-coaster just won't stop? Well...it hasn't! And I don’t think it will. And I'm feeling...I'm wondering...well...how much more of it can I take? I'm scared; I don't know what'll happen when I run out of strength, but...I know it won't be good."
Celestia grew sad and nuzzled Twilight again. "Terrible things happen when you run out of strength; I learned that not two hours ago. When I ran out of strength...I screamed at you and hurt your heart more than I dare imagine. But I don't think you will run out of strength, Twilight---you haven't. And...your emotional roller-coaster ends now."
The Princess said that very firmly, as if she was convinced it was true, and determined to make it true---but how could she be sure? "Will it?"
"Yes, it will," Celestia insisted. "You made a promise that you wouldn't let what the corruption does get to you, so the corruption can't touch you. And in Cloudsdale, the problem was me. The rain and the cold, and even your own town being in danger---you were prepared for all of that, and it wouldn't have slowed you down: I did. And I'm promising you right here and now, Twilight, that I am done making you tired and scared." Celestia paused and smiled. "It felt very good to say that, Twilight. Say, Pinkie, what was that special promise you and your friends have?"
"The Pinkie-promise?" Pinkie asked.
"Remind me again, how does it go? Cross my heart and hope to die---"
"...fly, stick a cupcake in my eyEEEEEE!!!!" Celestia screamed the word "eye" because she had accidentally stuck her own hoof in her eye.
After an awkward silence, Twilight finally said, "I did that my first time, too."
Celestia smiled, scooped Twilight up in her hooves, and held her close to her chest. She belted out a laugh that Twilight hadn't quite heard before, but it seemed like a wonderful laugh. "Oh, Twilight, we have so many feelings we're going to need to sort through and decide what to do with once all this is done, but I'm glad at least some of them are happy. And we will need to do something about them...but I'm not worried, because I know this much: when it's all over, we'll all still be friends."
Twilight loved being this close to the Princess, and hearing her happy was a very refreshing thing after everything they'd been through.
Twilight hugged her mentor back and said, "You know...I'd wish this moment could last forever...if it weren't for the fact that all of Canterlot is under the thrall of a---"
Loud clinking of metal against metal and angry snorting interrupted Twilight's sentence, but it was apparent that she was about to talk about this very thing: several corrupted royal guards were again trying to break into Celestia's chambers through the bars.
Celestia frowned. "I'll say this about Satallion: he's got perfect timing!" She quickly wove her radar spell and frowned again. "I should've sent that out the moment we arrived, but I---!" She looked down at Twilight. "I did the right thing," she quietly finished.
"Those bars will hold, right, Princess?" Applejack asked.
"They'll hold. Don't worry." She added, "Once the radar comes back, we'll have to set out and fight immediately. If there's anything we need to do to prepare, we should do it now."
Twilight began taking off her dried raingear and stuffing it into her saddlebag. "Let's keep these; you never know if they'll be useful, again."
"There's a scary thought," Celestia moaned. Twilight could well imagine that she was hoping that all the rain was behind her; Twilight knew the feeling of hoping something was behind her all too well.
One by one her five friends switched out and stuffed their raingear into their saddlebags, keeping their sweaters on to keep warm in the chilly night. Rarity was the last out, and she let out a little gasp. "Princess...you need something to keep you warm, too!"
"I'll just stay in spirit---"
Rarity interrupted: "That was the plan in Cloudsdale, and it didn't work out. I don't want to make the same mistake twice, and I know ex-act-ly what to do! Sundancer, is there are spare blanket in here?"
Sundancer came out from where she was hiding, carrying a blanket with her magic. Rarity quickly took the blanket and, using some surprising twists and knots, she quickly fashioned a large hooded cloak for Celestia. Celestia smiled. "Thank you, Rarity---I hadn't realized how cold it was until you put it on."
"I hope it serves you well, Princess."
At that moment, the radar came back. Celestia stared at the glowing orb for a few seconds, then said, "The southern district, near the borders of the city. We need to get moving."
Twilight thought aloud, "Will it be safer for us to teleport there, or should we go along the ground?"
After pondering the question for a moment, Celestia answered, "Either choice is dangerous. If we teleport, then Satallion won't see us coming, but he'll likely have many troops stationed around the core to defend it, and we won't know what we're up against until we see it. If we go along the ground, he'll see us coming, but we'll have a better chance of seeing what we're up against."
Twilight thought about it for a moment. "I wish I could say 'we're not taking any chances,' but the only choice we have is which chance to take...Let's go on foot. I'd rather not teleport into something I don't know about.
"But before we go," Twilight added, "Let's uncorrupt those guards." Twilight switched out, fired as many arrows as she could at the seething guards as they railed against the magical bars, and uncorrupted all of them. Celestia moved the bars so that the guards were inside them, and told them, "Stay here, and don't let corrupted ponies touch you---if they do, the corruption will spread back into you. And don't worry; my plan to rid Equestria of this evil is well underway!"
Celestia teleported herself and Twilight to the balcony, and Celestia went back into spirit form. Twilight braced herself for more running around and fighting, then looked down over the balcony and switched out with Rainbow Dash.
Dash flew to the ground, and it wasn't long before more guards were upon them---all of them were pegasi or earth ponies, which made Twilight wonder where the unicorn guards were. Twilight switched out and did her best to uncorrupt as many of the guards as possible. But there was a problem: instead of running away when they were cured, the guards immediately obeyed their training and tried to fight the other corrupted guards. That only served to quicken the corruption's spread. Twilight shouted to the guards, "Don't try to fight them; run! You'll lead them away from me, and then I can work on the Princess's plan to stop the corruption!"
The guards didn't need to be told twice by their Princess’s protege; they ran, and took the herd of corrupted ponies with them.
Twilight began running through the courtyard towards the castle gate, and now servants from the castle began rushing at them---butlers, janitors, ladies-in-waiting, gardeners, maids---all of them rushed at her. Fortunately, they didn't have the same battle training that the guards did: when a few of them were uncorrupted, they ran away and took the herd with them. Twilight felt like she really had the hang of it.
She rushed toward the gate and found it locked tight. Of course, she couldn't use her magic to open it, so she instead shouted, "Fluttershy, you fly us over this gate---get ready to send your animals out and get us a diversion."
Fluttershy switched out nervously, and when she had gathered a small flock of birds, she slowly peeked up over the gate, and saw the streets filled with corrupted unicorns---some of them guards, some of them nobles, but most of them just the common residents of Canterlot. Fluttershy gulped, and it was so quiet in the streets that her gulp echoed all over the city. Every head turned towards her and glared darkly. "Um...hi?" Fluttershy nervously said.
The unicorns charged the gate and began smacking it with all their collective magical might, but it wasn't enough to break the gate down. Fluttershy apparently decided to be brave, because she sent her birds away, and they cheeped and sung in-flight as loudly as they could. Every head turned as the birds flew overhead, and then the whole herd rushed away as one after them.
Rainbow Dash quickly switched out and flew to the south as fast as she was able. As they were flying, Twilight thought aloud, "This is where I grew up as a filly...at least the corruption hasn't redecorated the place while we were gone...!"
"Your parents live around here?" Applejack asked. "I met 'em at yer brother's wedding...it's sad to think they might be..."
"Let's not think about it," Twilight said aloud, just as she was pushing the thought of them being corrupted out of her head. "But...yes, they do live around here." The thought seemed to nag Twilight as she recalled that nothing was too low the corruption: Satallion had already tried freezing them to death, capitalizing on Celestia's phobia, and saying exactly the right things to get under Twilight's, Rainbow Dash's, and Pinkie Pie's skins. Doing something nasty with her parents---that was, unfortunately, right up the corruption's alley.
But what would it try? Making them yell at her that they never loved her? ...That would be disturbing, but easy to get over; Twilight knew full well by now that it would be a lie. Twilight had half a feeling that something far worse than that was on the horizon, but she pushed the thought aside before it overwhelmed her and tried to stay focused.
She asked, "Princess, where exactly is the core?"
"The reading came from very near the outskirts of town, almost at the edge, which seems very odd. At that location, there would be parts of Canterlot that would be outside the effective radius of the core; it doesn't make any sense to put one there."
"Unless," Rarity thought aloud, "There's more than one of them in Canterlot...!"
"Satallion hasn't done that yet," Applejack added. "If he's usin' more than one core, it's because he's got somethin' special in mind for Canterlot. I don't like the sound of that!"
More corrupted ponies began rushing out at them and charging them. They couldn't keep up with Rainbow, but they were appearing in front of them as well as behind them. She tried using her tornadoes, but they could only knock the ponies back so far before they began coming at her again.
Fluttershy switched out and sent more birds out. The whole crowd began chasing after the uncorrupted birds, and Twilight switched out and uncorrupted the stragglers that were still after them.
As the final enemies cleared away, Twilight looked around. They were pretty close to the edge of the city, close to one of the many cliffs that dropped straight down to the valleys below. And they were fairly close to the neighborhood where her parents lived, too. But there was no core in sight. "Are we going to need to start checking the buildings?" Twilight asked.
"I'm afraid that might be necessary," Celestia sighed.
"Nuts! The corruption's getting smarter!" Pinkie Pie moaned. "Hiding the core in a plain old regular pony's house is the perfect way to keep us from finding it! There's so many of them that we'll have to look at---it’ll take forever!!"
"They may have other tricks for keeping it hidden as well; I've been trying to sense the core's general location, but so far, I keep getting the east side of Canterlot. That could be the other core's location, but...I should at least be able to sense this core if it's nearby."
"Um...you don't think maybe the core, uh...moved?" Fluttershy asked.
"If they've attached a core to a cloud and have a pegasus moving it around," Dash thought aloud, "They could do that. They did it with Cloudsdale, but...how big across is Canterlot?"
"About six miles across," Twilight answered.
"I'm not sure a pegasus team pushing a cloud could cover five miles in the fifteen minutes it took to get to here from the castle."
"They could be using some kind of stealth magic to keep this core hidden," Celestia suggested. "If only there were some safe place where I could send out the radar again; then we could narrow it down---even if we didn't know exactly which house the core was in, we'd probably have our choice of two or three---"
The loud roar of two unicorns bellowed from the very edge of the cliff. The dark, booming voice of Satallion echoed through their voices, but something familiar was in them as well. Twilight tried to stifle the thought that they might be her parents, but turned her head in dread---and it was her parents!
She slowly walked closer to her mother and father, both of them standing very near the cliffs, eyes blazing red, and starting at her darkly.
Twilight snorted, trying to steel her heart against whatever she’d be put through this time. "Look," she insisted, "It doesn't matter what you say; I'll know it's a lie!"
Satallion chuckled back. It was strange and unnerving to hear that laugh out of her parents' mouths---while they were still glaring at her so angrily. "This isn't about what I say, unicorn. It's about what I'm about to make your parents do. The Spell of Unity may protect you from death, but it doesn't protect your parents. And it's a long way down from this cliff."
Twilight's face went pale at the thought.
Satallion didn't slow down; he struck while the iron was hot. "Terrifying, isn't it: these two ponies who you love and cherish, gone forever! That is what I will do to you unless you disband the Spell of Unity and surrender to me---unconditionally!"
For a moment, Twilight was too scared to think. She realized after a few seconds that she should be thinking of something, anything, that might get her mom and dad out of this!
"Why are you even fighting against me?" Satallion continued. "Name one objective problem that my so-called 'corruption' creates. It doesn't hurt the health of those who have it---if anything, it makes them more active. It doesn't disrupt your economy or weather. It doesn't prevent you from having children, or from eating or producing food. What possible motive have you to fight me? Besides, it's not really that bad to be 'corrupted', anyway. Don't be so afraid to give in."
Twilight actually began to believe Satallion for a moment, then remembered that Ponyville was hit with a super-storm on account of the corruption, so it did negatively impact the weather. He'd negatively impact anything---the economy, health, nature itself---if it would help him get to them. And while the ability to love your family, friends, and neighbors might not be an objective benefit, it was still worth fighting for.
So Twilight was afraid to give in...but could she watch her parents fall to their deaths? Her nerves were already frayed, and her heart was so tired...would this make her run out of strength? If she did, wouldn't Satallion win? So...either way, Satallion had already won. ...Unless Twilight had the strength within her to keep fighting, even with her parents dead.
Twilight didn't like the sound of that, but she made her mind up that she would have the strength. She was scared, tired, and very, very hurt. But she wouldn't give up; she'd find the strength within her.
"I'm a patient demon," Satallion continued, "I can wait for your answer for a looooong time." After a pause, Satallion laughed. "Or are you actually thinking about sacrificing your parents? What a ruthless move that would be! Would you really be that different from me if you chose that? Oh, it makes a kind of sense: they're older than you, and you will probably one day outlive them and have to bury them. Why delay the inevitable? Why not just let them perish at my command?"
Twilight hated the sound of what Satallion was saying, precisely because it made an abominable kind of sense. It was a hard choice; if she gives in, she'll be filled with hate and become just like Satallion. If she doesn't, then she sacrifices her parents---an action that takes a special kind of coldness of heart. A coldness of heart that's not unlike that of Satallion. Had Satallion already won, just by presenting Twilight with this choice?
Satallion interrupted Twilight's thoughts with another cruel laugh. "Just make sure your parents don't die of starvation before they die of their fall."
Twilight scowled. She didn't want to resign herself to the fate of losing her parents, and began to realize that another part of having strength is to refuse to resign yourself to any despair---she decided that she'd use the time she had to think of something, anything, to save her parents.
But the fact that she had this time made Twilight wonder: just why was he giving her so much time to decide? Was he trying to drag things out with more suspense? ...The suspense was painful, but less painful than actually losing her parents would’ve been. And Satallion always goes for the most painful thing that he can do; when he had the choice between causing Celestia pain by maintaining the storm and setting her back by sending pegasus troops after her, he chose pain over practicality. So why hadn't he already sent her parents over the cliff? Would forcing Twilight to surrender be more painful than watching her parents go over the edge? ...Twilight realized that that wouldn't be more painful for her, and she briefly was tempted to give in for that very reason. But she stopped herself: it would be more painful to see her parents die, but that didn't make it the right choice. Besides, she can't love anypony while she's corrupted, and, as ruthless as it might sound, what good were her parents---or anything, for that matter---if she didn't have the ability to love them? It was true, but it was a sickening thought on so many levels.
Wait---not having the ability...? What if Satallion hadn't sent her parents over the edge because he plain and simple didn't have the ability to do so? ...Twilight recalled how, when they were fighting Rainbow Dash, Satallion never had her run away from them. Having her run away would've been the most intelligent and painful solution; without her, the Elements of Harmony would be incomplete, and they wouldn't have been able to make any progress against Satallion---they’d have had to watch him get more and more powerful, and they’d have been helpless to do anything to stop him. That would’ve been extremely painful. And Satallion had to have known by then what keeping Rainbow Dash away from them would’ve done, both to them and their efforts. And while he had sent crowds of pegasi after them in Cloudsdale, he had never been able to direct the specific movements of his thralls---not even when he could’ve used them to strike a decisive blow that would've won him this war forever. As powerful as his magic was, he hadn't yet displayed any ability to command his troops directly. So he probably didn't even have the ability to make good on his threat, as strange as it sounded.
The one difference between the fight with Rainbow Dash and this conversation was that Twilight had been actively fighting the corrupted Rainbow Dash, but she hadn't yet begun to fight her parents. So, just in case being in combat had anything to do with it, Twilight fired an arrow at each of her parents.
Just as Twilight had hoped, they charged, rushing towards her---and, most importantly, away from the cliff. As they charged, they roared, "Fine. I'll make your own parents pound you into the dust until you are in so much pain, you'll wish I would finish you! THEN I will send your parents to their deaths!"
Twilight's stomach tied itself in knots at the thought that Satallion might be telling the truth. The rational thing to do, if he had the ability to send her parents over the edge, would be to send them over before she could uncorrupt either parent. But maybe he was acting irrationally! Twilight tried to push the thoughts aside and focus on the battle; she knew her parents were both powerful with their magic, so she didn't know quite what to expect.
In some ways, the battle felt like fighting two Trixies: they used the same wave-magic that Trixie, the Manticore, and Gilda had used, and were also able to fire arrows of darkness back at Twilight. She did her best to dodge and kept firing arrows at her parents.
It dawned on her that this was also like fighting the Cakes; as soon as she managed to uncorrupt one of them, the other could re-corrupt him or her. She didn't want that to happen here, but she realized she had a lot more combat options available to her this time, because all her friends were there. And she'd learned her lessons from before.
So she tried to avoid shooting either of her parents too much more than she was shooting the other; she made a point of getting them both close to uncorrupted, but not quite there. Then she shouted, "Applejack! Use your earth pound!"
Applejack switched out, got as close as she could to Twilight's parents, and pounded the ground. The impact stunned both parents and knocked them a little bit backward. Twilight quickly switched out and finished uncorrupting both her parents.
Twilight felt the adrenaline and suspense drain from her system as a wave of relief swept over her: she had won that fight, that conversation, and both her parents were still alive! She had successfully proven that, even when Satallion presents her with a difficult choice, she could find a third option and get herself and her loved ones out of danger. That lesson alone was incredible relief to her, almost as much relief as seeing her parents' eyes return to normal. They looked like they were full of regret, but that was a wound that could be easily healed, especially in comparison to what her family had been threatened with.
"Twilight...we're so sorry!" her mother began.
"Don't worry," Twilight insisted, rushing in for a hug. "It's over."
After a few seconds, Rainbow Dash spoke up: "Wow, Twilight...you must have nerves of steel if you've got what it takes to fight when Satallion has your parents on the edge of a cliff!"
"I don't have nerves of steel at all," Twilight insisted---probably a little more grouchily than she should have. Hoping her tone alone would correct it, she continued softly, "I realized that Satallion couldn't make good on his threats; we've done a lot of fighting against corrupted ponies, and never once has he actually given them specific marching orders. So I figured it just wasn’t one of his abilities to actually send Mom and Dad over the cliff."
"You mean his threats were empty all along?!" Rarity gasped.
"That big. Dumb. MEANIE!!!" Fluttershy roared.
They heard a snort behind them, and saw more unicorns charging them. Twilight's parents immediately combined their magical might and put a force field up, one that looked almost exactly like the force fields Shining Armor or Twilight herself often used. The corrupted unicorns rammed into the force field, but Twilight's parents made sure it held.
The force field left them trapped, but safe. At the very least, it gave them time to think. So Twilight thought, trying to remember what they had been doing---then she realized that there was supposed to be a core nearby, and they needed a safe place to send the radar out from to find where it was specifically. But her parents' force field was just the safe place they needed!
"Princess, the radar! We can send it out from here!" Twilight thought aloud.
Celestia switched out quickly and sent her radar spell out. Twilight's parents were surprised to see her, but she whispered, "Don't bow; concentrate on keeping the force field sturdy."
Twilight turned to her parents and nuzzled them again. "Mom, Dad...this might be the last chance I get to talk with you. I'm so glad I got to see you, and...and...it was scary to see him make you stand on that cliff...I almost gave in to him, but...I didn't." Unable to think what more to say, she just said, "I love you guys."
"We love you, too, Twilight," her father answered, kissing her forehead. "We've missed you a lot since you moved to Ponyville, but we know you've really put down roots and found your place there."
"We're so proud of you," her mother added.
Twilight just stood there with her head nestled between her parents' heads for a moment. It felt good to be surrounded by so much love, even if there were unicorns smashing against the force field all around them. Twilight almost felt like her heart was beginning to heal; she'd been through a lot, but just being around her parents gave her hope: it was enough to let her know that, even though she'd been through so much, it was nothing that being surrounded by love couldn't fix.
After a few minutes, her mother finally said, "Please, Twilight---tell us what's going on! You're with the Princess, and you said something about doing a lot of fighting...you must know something!"
"Oh, where do I even begin?! ...This corruption is evil magic that's been cast on all of Equestria by this demon named Satallion. He's trying to take over Equestria with it, but it has weaknesses. The Princess realized what was happening, and she cast this Spell of Unity on me and my friends from Ponyville so that we'll be immune to it. The Spell of Unity usually only allows one of us to be in physical form at a time; the rest of us are in spirit form. There's exceptions to that; the Princess can switch out whenever she likes without affecting the six of us, and she can pull all of us into physical form for a few minutes so that we can use the Elements of Harmony.
"And we need the Elements to destroy these magical core-things that the corruption relies on; if a core is destroyed, then all the ponies in the same city as that core will be freed from the corruption. We're trying to find Canterlot's core now using the Princess's radar spell. It told us the core was here about twenty minutes ago or so, but when we got here, we couldn't find it right away, so we're using the radar again to see if we can narrow it down."
Celestia shook her head. "If the core were within a mile of here, the radar would've come back, by now."
Applejack asked, "I don' know much about magic, but d'ya s'pose Satallion's figured out how to make yer spell lie to us?"
"I’m not sure," Celestia admitted, "But those cores give off a great deal of negative energy; it would be impossible to conceal one."
"Wait...Mom, your special talent is detecting and analyzing magic; maybe you can help us figure out which is the real core?"
She nodded. "I'll take a look when the spell comes back. But we'll need to wait for it to come back from all the different places in Canterlot before we can be certain."
After a few more minutes, the radar returned. Twilight's mother walked up to it and checked it over. "This looks like it's picked up a massive negative energy signature. I think this is the real thing, but let's wait and see."
Several mintues later, Celestia finally said, "If there were anything else in Canterlot for the radar to pick up, it would've come back by now. So this signal is definitely where the core is."
"So there's two possibilities," Twilight's father thought aloud. "Either the core you were looking for self-destructed, and they have two cores in Canterlot, or..."
"Or the core they have can move on its own!" Twilight finished.
"That weather-golem that was made out of the last core proves that they can do more with the cores than just have them sit there," Rarity added.
"Oooo, I hope it doesn't turn out to be another nasty, scary monster like the last one!" Pinkie whimpered.
"What else can it be?" Fluttershy asked.
"I wish we didn't have to find out!" Pinkie moaned.
"So...where do we need to go next?" Twilight asked.
Celestia answered, "According to the radar, the core hasn't moved from the east side of Canterlot, yet. But, Twilight...there's something we need to talk about before we go. You've been through a lot, today, and Satallion putting your parents in danger was...a new low. I'm very worried about you, right now; I think you should stay in spirit form and get some rest, again, the way you did in the forest."
Twilight looked from the Princess to her parents, gave them another quick nuzzle, then looked back at Celestia. "I just got some rest, Princess. More than you would believe. I can keep fighting."
Celestia looked at Twilight with concern for a moment, then smiled and switched into spirit form.
"We can turn this force field into a repulsor nova to knock these other unicorns away; that'll give you a few seconds so you can run," Twilight's father said.
"We'll put up another force field once you're clear," her mother added. She put her hoof on Twilight's cheek. "Come back to us in one piece, dearie."
"Don't worry; I will." She gave her parents one last goodbye kiss, then they fired off their repulsor nova. Rainbow Dash switched out and bolted to the east, not looking back at all.
As she flew through the air, dark arrows came flying up at her. She was too agile to get hit, but there were a lot of arrows to dodge.
Twilight looked down. "Those arrows are coming from some kind of elementals, and there are a few unicorns that're shooting arrows, too!"
"At a guess," Celestia thought aloud, "It's only unicorns with strong affinities for magic that are capable of firing arrows of darkness."
Applejack gulped. "Ain't there a lot of powerful unicorn wizards in yer royal guard?"
"And at my School for Gifted Unicorns," Celestia added. "And at the Canterlot Research Institute where Twilight's parents work---I have to admit, the odds are stacked against us, but nevertheless, we must try."
"I'm starting to wonder why we haven't seen some of the tougher members of the royal guard come after us," Twilight said. "I mean, we've still not seen my brother, or Princess Cadence, or even any of the elite guards."
"Or Princess Luna," Celestia cut in.
Fluttershy audibly whimpered. "You mean...Nightmare Moon is back?"
"That's a possibility we just have to face," Celestia sighed.
Rainbow Dash snorted as she kept dodging arrows. "All of that probably means Satallion's got something special planned. I don't like the sound of it..."
"And if he can move his core, that means he can lure us wherever he wants us to go!" Rarity added.
Pinkie gasped. "He must've had us come to Twilight's parents just so he could tease her with his meanie-mean-pants plan to trick us into thinking he could make them jump off the cliff and go splat!"
"...Our promise not to let what the corruption does get to us is going to be really, really important, now," Twilight said. "It's not enough to just fight us; Satallion won't use a plan that won't make us hurt. That's his strength, but maybe it's also his weakness."
"All of this is making me wonder..." Celestia began to philosophize. "He can't give his troops direct marching orders, his troops can't run away or think while they're corrupted...it's almost as if some forms of stupidity are inherent to his power, and to his very being."
"Just like a lot of how hate is inherently stupid in a lot of ways," Twilight thought aloud.
"It's like Satallion and everything about him and his corruption are made of hatred---the fingerprints of hate are on everything he does."
"Just where in the eastern district is the core?" Rainbow Dash interrupted; they were getting very close to the eastern district.
"The signal came from about the train station."
Rainbow Dash veered downwards, and found that the station was seething with elementals. She blasted them back with wind and let Twilight switch out. She fired as many arrows as she could, but she couldn't help but take some hits, as well. If only there were a way to keep the elementals from coming at her all at once!
"Rarity!" Twilight shouted as she took another hit. Rarity switched out and threw out a couple of crystal prisons. She found out suddenly that, when she threw out a crystal prison, the elementals near the prison stopped firing at her, and instead fired at the prisons to free their trapped comrades. That bought Rarity the few seconds she needed to touch a few heart-crystals to Twilight's spirit-orb and heal her. Rarity threw out a few more crystal prisons before letting Twilight switch back out. Twilight made quick work of the distracted elementals, but she did need Rarity to switch out and freeze a few more of them a few times before the battle was over.
Twilight looked around. There were no corrupted ponies or elementals in sight. It was far too quiet. She took a few steps toward the train station and peeked around the corner. There was her brother---and Princess Cadence.
"Took you long enough," Satallion said through their mouths. "It's high time---"
Twilight didn't wait to hear what Satallion had to say; she immediately began firing arrows. Shining Armor created a force field of his own, and Princess Cadence began flying overhead and blasting them with magic from above. Twilight did her best to dodge and recalled the first real fight she'd had, against Fluttershy, where she had discovered to her horror that she couldn't fire her arrows up, but only parallel to the ground. Now Cadence was hovering out of her striking range!
Fluttershy switched out and tried sending birds at Cadence. Sure enough, she forgot about the battle, grabbed a bird between her hooves, and let the corruption seep into it. She was still too high up for Twilight to hit her, but the bird had lured her a bit lower. So Fluttershy sent another bird at Cadence again, this time again a little lower, and Cadence was lured still closer to the ground. Fluttershy kept this up, and finally, Cadence was at ground-level. Twilight began blasting her with as many arrows as she could, and Cadence immediately took off.
Twilight was a little surprised that Shining Armor hadn't fired a shot or even really done anything; it was actually a clever tactic to stay hidden behind his forcefield until he was needed. Cleverer than corrupted ponies usually were, which was a scary thought to Twilight. She tried to reason out what exactly the rules and limitations were, and then she realized that the real rule was that, when corrupted ponies were in combat, there always had to be at least one that was doing something to attack. As long as Cadence was attacking, Shining Armor could stay hidden inside his force field. ...Though it wasn't like Shining Armor to hide from a fight when the chips were down...
It dawned on Twilight that it was very possible that Satallion wasn't just keeping Shining Armor inside that force field to make the battle more difficult and unpredictable for Twilight: he might be doing it to shame Shining Armor by making him fight like a coward.
Twilight pushed the thoughts aside as Fluttershy lured Cadence back down to ground level. She wanted to see just how Shining Armor would react if Cadence were incapacitated, so instead of firing her arrows, she shouted, "Rarity, crystal prison!"
Rarity hurled a gem at Cadence while she was at ground-level, too low for her to get injured from the impact with the ground. Cadence was frozen in rock, and as Twilight predicted, her brother dropped his force field and charged at the crystal to try to break it with his hooves and magic. Rarity jumped out of his way and tried freezing him in a crystal prison as well, but the gem simply bounced off his armor and shattered.
"Pinkie, try your party cannon!" Twilight shouted. Pinkie switched out and covered the stallion with fly strips, and he struggled against his bonds for a moment. Twilight took that opportunity and switched out, firing as many arrows as she could at her brother. For a few seconds, it seemed to be working, but he quickly ripped his bonds up and whirled around. He fired an enormous arrow of darkness at Twilight out of his horn---so huge, she thought it was more like a spear or even a ballista bolt. Twilight gasped, as she didn't have time to dodge before the bolt was going to hit her---but Applejack switched out and took the hit instead. She was knocked to the ground, and Twilight quickly switched back out and tried to think of something...but it was too late: Cadence was freed of her crystal prison, and Shining Armor was once again hiding behind his force field.
Fluttershy switched out again and began luring Cadence to the ground again, and when she was near enough, Twilight shouted for Rarity to use her gems again. She did, and that again lured Shining Armor out of his force field.
This time, Twilight had a better idea of what to do. "Party cannon!" she shouted, and Pinkie had Shining Armor again wrapped in fly strips. Twilight knew that wouldn't hold him for long, but she also realized his armor---while it was his strength---was also his weakness. If he were to fall over, especially while he had fly strips on him, then it would take him a while to get back up. So she shouted for Rainbow Dash to use a tornado on him to knock him over, and sure enough, that kept him off his feet for long enough for Twilight to uncorrupt him.
"Sis!" he shouted. "Are you okay?!"
"I'm fine," she answered. But when she saw that he was about to touch Cadence, who was still corrupted and still locked in crystal, she screamed, "Don't touch her! The corruption spreads by touch!"
Satallion replied, through Cadence's mouth, "Oh, touch me, my husband! I'm just dying to feel you---"
“Don’t listen to him!” Twilight interrupted. She knew Satallion was about to say something raunchy to get to her brother, or maybe to insult the sanctity of their marriage, and didn’t want to see or hear that happen.
“Ugh…Twilight, what’s going on, here?” Shining Armor asked.
“Your sister has betrayed us!” Satallion made Cadence shout. Twilight’s face went white, terrified that her brother might believe whatever lie Satallion was about to weave. But one look at his face told her that he wasn’t buying it for a second.
“Twilight, whatever it was that you did to get me back to normal---please tell me you can do it again for Cadence!”
“I can, and I will,” Twilight answered. “But I have something to say to Satallion, first.” She stepped up in front of the crystal prison so that Satallion could see her face through one of Cadence’s eyes, but not far enough so that he could aim Cadence’s horn at her to blast her with magic. Steeling herself for this conversation, she glared into the very eye of evil, itself. The firmly said, “You are not gonna win this war! You’re powerful, but our unity and friendship more powerful. You don’t give up, but neither do we! And you’re smart, but we’re smarter---and no matter what you put me through, no matter how much you try to mess with my head, I won’t let you win! You can make me miserable...but you can’t make me stupid. Not anymore.”
With a sneer that could cut granite, Satallion answered through Cadence’s mouth, “That’s quite alright, unicorn. Miserable is enough for me!”
Twilight snorted and fired arrow after arrow into Cadence’s body until she was uncorrupted.
For his part, Shining Armor had a look of horror and righteous fury on his face. He couldn’t stomach the thought of this evil hurting his sister and using wife---and using him! After a few seconds pondering the horror of it, Shining Armor began to weave his magic to break Cadence out of her crystal prison.
“Twilight! Shiny!” Cadence asked frantically. “Are you all right?”
“We’re fine,” Shining Armor answered, gently lifting Cadence out of the crumbling rock and setting her down safely. They rubbed their heads together to reassure themselves that they were all right, and after a few seconds, they turned to Twilight, and Shining Armor asked, “You seem to know what’s going on, Twilight. Please, tell us what’s happening to Canterlot!” He said it with more than a little shame; as captain of the guard, he should know more than Twilight about any threat to Canterlot---but all he knew was that dark magic had taken control of him and his wife, and forced them to fight his sister and her friends.
The rumbling of a hundred ponies’ hooves thundered towards them. Shining Armor quickly formed a forcefield around them, and not a moment too soon: corrupted unicorns, many of them part of Shining Armor’s guard, charged at the forcefield and began to smack it with hooves and magic to try to break it down and attack them. Shining Armor was more than able to keep the forcefield steady against the onslaught, but it was still a very disturbing sight to see all these corrupted ponies trying to attack them.
“It’s just as awful to see the effects of the dark magic from the outside,” Cadence moaned. “I can’t stand to look at the faces of our citizens, our servants, our friends when they’re like this!”
“Don’t look at them. Look at me,” Shining Armor insisted. The two lovers looked into each others’ eyes for a few seconds, then kissed. From that moment on, Cadence didn’t take her eyes off of her husband.
“Please, Twilight, tell us what’s going on!” Shining Armor asked again, reinforcing his forcefield. “If there’s even the smallest thing I can do to help fix all this, I’ll do it. It’s my duty to Canterlot!”
Twilight sat down. “There’s a lot to tell, Big Bro...this is all the work of a demon named Satallion; he’s trying to take over Equestria, and he’s created this corruption to do it. Whenever a corrupted pony or animal touches a pony who’s uncorrupted, the corruption spreads.
“The Princess has a plan to stop it; there’s an ancient spell called the Spell of Unity, and she used it to make me and my friends immune to the corruption. Only one of us can be in physical form at once, and...well, there’s a lot more to it that we’re figuring out as we go.”
Suddenly, it dawned on Twilight that Applejack was still injured from taking a hit for her, so she gasped and said, “Rarity, can you heal Applejack? I’ll keep explaining while you heal her…” Rarity switched out and began rifling through her bag for as many heart gems as she could, and Twilight continued to explain: “Somehow, this corruption magic can only work on any given living thing if something called a ‘core’ is close enough to it. A core is this...weird purple swirly energy thing, and we can use the Elements of Harmony to destroy it. And if we do, then all the ponies in the same city as the core get cured. The Princess keeps sending out this radar spell to find it---”
“Wait---Princess Celestia is with you?”
“Yes,” Celestia answered, “I am here, in spirit form. Don’t bow; focus on keeping the forcefield up.”
Shining Armor did as he was told, but he insisted, “Please accept my deepest apologies for my failure to keep Canterlot safe from this evil. I’m prepared to step down for this lapse---”
“This is no personal failure on your part, Captain,” Celestia insisted. “The corruption is very powerful magic that completely overrides free will; neither you nor any pony affected by it can be held responsible for their actions.
“Rarity, there’s no time to lose. I’m going to send off the radar again.” Celestia popped out into physical form, which was difficult in the cramped quarters inside the forcefield. But she sent the radar out and went back into spirit form.
Twilight kept explaining, “We’ve already destroyed three cores: one in Ponyville, one in Everfree Forest, and one in Cloudsdale. The Princess knew there was another one somewhere in Canterlot, so we came here, and we’ve been trying to track down the core here, but it...keeps moving. At least, we think it keeps moving; the radar keeps coming back to us from a different place every time we send it out, and when we finally get there---there’s no core. Which is really weird, because cores normally can’t move; they usually just sit there.”
“Now that Shining Armor is with us, I’d like to propose a new strategy,” Celestia cut in. “Captain, maintain your force field, and keep maintaining it while I teleport you and Cadence along with the rest of us to wherever it is the radar leads us. Even if the core isn’t there, at least we might be able to get some answers about why the radar keeps leading us to places where the core can’t be found. We’ll be going in blind, but your forcefield will give us extra insurance against whatever Satallion has planned.”
Noting the cramped quarters, Shining Armor expanded his forcefield outward in a repulsor nova to push the attacking ponies away, much as his parents had, and he re-cast a larger forcefield.
“How hard is it, Twilight?” Cadence asked.
“...How hard is what?”
“How hard is it to destroy a core once you’ve found one?”
Twilight sighed, knowing the answer wasn’t what Cadence wanted to hear. “Every core we’ve come across was guarded by something---an elaborate maze of caves, a powerful unicorn mage---one of the cores was even somehow turned into an armed golem of some kind. This one’s got to be guarded, too, and we won’t know by what until we see for ourselves.”
Cadence swallowed hard, and her husband gave her another kiss. “This time, you’ve got powerful unicorn mages on your side,” Shining Armor pointed out.
“No,” Celestia insisted. “The corruption spreads far too easily. In any other battle, you’d be the most valuable asset we could ask for, but in this battle, you’d be a liability. You mustn’t try to fight; if you fall under the corruption’s control, we’d face both you and whatever is guarding the core.”
Twilight switched back out and nuzzled her brother. “She’s right; it’s too dangerous. And I don’t want you to fall under Satallion’s control, again. If you’re going to do anything to help us, it’ll have to be from behind your forcefield.”
For a moment, Shining Armor stared at his sister, scanning her face. “I...I understand, Sis, but...your face...I’ve never seen you look this tired, before. Just what has this demon done to you?”
Twilight didn’t want to remember it. She shook her head. “None of that matters, now.”
“Twilight, I want to know what this demon is capable of, how it thinks, and how it works. And I want to know just what his crimes are.”
Twilight sighed. “He...he always knows exactly what to say to get under your skin. He did it to me, and to two of my friends. He had me so confused for hours that...that I felt like I was going to get sick. But that’s not the worst part...the worst part is, he had Mom and Dad standing at the edge of the cliff in the southern district, and...and he told me he’d make them jump off if we didn’t surrender!”
Shining Armor’s jaw dropped, and a fire lit in his eyes. He was barely restraining his rage against this evil that was hurting his family so deeply and so horribly. Finally, he hissed through his clenched teeth, “I...am going...to break...his neck!!!”
“Don’t worry, Mom and Dad are okay---I figured out that he can’t give specific commands to ponies he controls, so I didn’t give in. But...it was still the worst moment of my life.”
Shining Armor and Cadence each went close to either side of Twilight and rested their heads against hers for a moment---for good measure, Cadence spread her wing over Twilight’s back. They didn’t say anything, and that was alright---Twilight felt like she was drawing strength and comfort, just by being held by two ponies who had nurtured her and helped make her the mare she was today. Even with the backdrop noise of snorting unicorns railing against the forcefield, Twilight felt like the fatigue in her was slowly being washed away; even though she’d been fighting and running and thinking and worrying all day, she would have the strength she needed for the next battle. That was all that mattered.
After a few more minutes, the radar came back. Celestia switched out into physical form, studied the magic that had returned for a moment, then gasped. “Canterlot Castle...? …There’s no time to wonder why. Are you ready, Shining Armor?”
“Always ready to serve my Princess, castle, and nation!” He glanced at Twilight, and added, “And family!”
Celestia began the teleportation spell, and they winked out of existence.
The next thing they knew, they were surrounded by corrupted ponies on all sides---unicorn, pegasus, and earth pony guards, castle servants, and looming large above them was Nightmare Moon---her eyes were blazing red, and a core was woven into her mystical hair!
“Luna---NO!! Not again!” Celestia cried.
Nightmare Moon sneered down at them. “So predictable,” she shouted. Again, her voice sounded like a mix of Luna’s and Satallion’s; it was clear that Satallion was talking through her mouth. She landed, walked up to the forcefield, and with the same horrible look Cadence had given Twilight, she chuckled, “Checkmate, Tia.”
“What’re you talking about?” Rainbow Dash snarled, switching out and getting up to Nightmare Moon’s face.
“She’s right,” Celestia softly said.
“What?!” Fluttershy asked.
“Ya cain’t mean we’re just givin’ up after everything we’ve done!” Applejack shouted.
Celestia shook her head. “There are far too many corrupted ponies to fight; we’ll never be able to survive a battle with them---”
“Even with those ‘extra lives’ your precious Spell of Unity grants you!” Nightmare Moon sneered.
“We can’t just give up,” Shining Armor insisted. “Let me use a repulsor nova to clear them out. I’ll---”
“Oh, I’ve already thought of that,” Nightmare Moon laughed. “I have plenty of troops out of line-of-sight of your magic. You can’t win! And you can’t linger here, either: even your forcefields won’t hold for long against the combined might of my little ponies!
“Your pathetic attempts to fight me will make no difference in the end---everything you’ve done was taken into account in my plan! You can’t win!
“Not that I expect you’ll be wise enough to give up; you always were the dumb one, Tia. And the spoiled brat who would never even do as she was told! I can see everything in Luna’s mind, and I can tell you right now: she never loved you! She only ever stayed with you out of a misguided sense of filial---”
Twilight saw that Satallion was now trying to get under Celestia’s skin. It wasn’t enough to trap them in a tactically unwinnable situation; he had to hurt his victims in the worst way possible, too! Twilight blurted the first thing that popped into her head: “Princess, cover your ears!”
The split-second after Twilight suggested it, she realized that it was a childish solution---it was hiding. Shouldn’t any adult have the courage and wisdom to refuse to believe his lies? But to Twilight’s surprise, Celestia actually did it: she got down on the ground and plugged her ears with her hooves. Twilight gave her blurted advice a second thought, and realized that it wasn’t such a bad piece of advice, after all: there was nothing Nightmare Moon had to say that Celestia needed to hear, and there was no way out of the forcefield except to teleport away. And Twilight didn’t want to do that just yet; she had managed to think of something when her parents were in danger, so maybe she’d think of something now.
Twilight’s train of thought was interrupted by what she thought she saw, for a moment: she could’ve sworn she saw Celestia stick her tongue out at Nightmare Moon! If she had blinked, she’d have missed it. Strangely, she felt comforted by the sight of such a childish action---though Twilight was confused for a second about why it felt comforting. Then she realized why it was a comforting sight: it meant that the Princess was still herself! She liked being silly every now and again, and it was one of the things that made her who she was. And despite everything Satallion had put her through---rain and terror and guilt---no permanent damage had been done to her mind. That was a massive relief to Twilight!
Nightmare Moon apparently didn’t miss it. She shouted, “You are all foals! Why don’t you just grow up?!”
Applejack shot back, “Listen you, I got a comeback for you involving the words ‘Why don’t you just’ and ‘up’, but I ain’t gonna say it in the presence of two princesses!”
“Thank Celestia you’re not that uncouth!” Rarity chimed in.
Shining Armor snorted. “Fine. We can’t win this fight. Princess, can you teleport us away? We’ll find a fight we can win, and---”
Nightmare Moon screeched with horrible laughter.
Pinkie moaned, “Ooo, I hate that kind of laughter!”
Nightmare Moon continued, “You little foal! Don’t you realize that won’t do you any good? You’ll be no better off than you were when you came to Canterlot if you can’t destroy this core! Canterlot is mine, and soon all of Equestria will be mine! Flee now, and you’ll have gained nothing!”
“Not true,” Twilight shouted, switching out. “I’ll have my brother and foalsitter back, and even though I don’t expect you to understand why, that’s the most valuable plunder I can take away from you. And you make no mistake: we’ll find a way to beat you, whether we think of something here, or think of it someplace else!”
Twilight turned to Celestia, and she opened her ear just enough to hear her. “Come on, Princess. Let’s teleport out of here while we still can.”
Celestia sadly nodded, but took one last look up at Nightmare Moon before she teleported away. “Luna...I don’t know if you can hear me, but I will come back for you. I promise you that.”
Suddenly, two ponies popped into existence next to Shining Armor and Cadence---it was Twilight’s parents!
“I sensed that things weren’t going well,” Twilight’s mother explained, “So we came to see if we could make a difference.”
Nightmare Moon laughed and glared at Twilight. “So, your ‘family’ is complete, my little pony? Ha! What difference does it make?! You keep implying that I don’t know what love is. I’ll concede that I don’t, but there is something I see that you don’t, as well, and I think you’re finally starting to see it:
“Love makes no difference!! I can, and I will hold Canterlot indefinitely, and you’ll never be able to make yourselves stronger than you are now---your Spell of Unity cannot hold any more ponies! Any army you raise elsewhere in Equestria won’t be able to help you; they won’t be immune to my magic! You will never be able to overcome my position here! But I can, and I will keep getting stronger, as more and more ponies come under my thrall. The cores you have destroyed can be replaced more easily than you’d dare imagine! And the love you have between you and your friends, you and your family, you and your Princess, can never overcome my power! If it could, then tell me this: why didn’t it? Why didn’t dear, cute, demure, vulnerable little Fluttershy apologize to you and kiss and make up when you called to her, the first time you saw her under my thrall?”
Twilight remembered that moment, the first time the corruption really yanked at her heartstrings---then she realized that, just by pondering what Satallion was saying, she was taking the first step in the direction of letting Satallion’s words get to her. So that was it---she wasn’t listening, anymore. She had to get her mind off of it; she had to focus on what they were doing.
What were they doing? They were about to teleport away and try to come up with a plan to retake Canterlot---but if Satallion wasn’t lying, then retreating here would get them nowhere---it might even undo all the hard work they’d spent the whole hard day doing, if Satallion somehow used the resources in Canterlot to replace the cores they’d destroyed. And if he replaced the core in Cloudsdale, the setback would be horrible! And, since he knew about Celestia’s phobia of rain, he’d make taking Cloudsdale back a priority. Twilight’s face went pale at the thought.
“Princess, don’t teleport away---we need to think of something, and we need to think of it here and now.” Twilight looked at her parents and her brother and Cadence, trying to think of what she had to work with. Suddenly, something clicked in her mind: if her parents could put a forcefield around themselves, Shining Armor, and Cadence to keep Nightmare Moon out, and if Shining Armor could put another forcefield around the castle courtyard to keep Nightmare Moon in and keep her reinforcements out, then they might just stand a chance!
Twilight barked out, “Mom, Dad, put a forcefield around yourselves, Shining Armor, and Cadence! I have an idea!”
Twilight’s parents immediately obeyed, and Shining Armor smirked righteously. Twilight began to say, “Now, Shining Armor, use your forcefields to keep---” But her brother immediately saw what Twilight was planning, and had already put his forcefield up.
“Give me strength, and we can do this,” he whispered to Cadence. He turned to Nightmare Moon and shouted, “You’re not going anywhere, demon! Give ‘em hell, Twilight!”
“I AM HELL!!!” Satallion shouted back, beginning to brandish Nightmare Moon’s terrible magic.
Twilight began firing arrows at Nightmare Moon, and they seemed to have some effect, but the core was pushing back: while Twilight could remove some of the corruption from Luna, the core kept putting it back.
Nightmare Moon let her mane sweep in front of her, and began hurling lightning at Twilight. She did her best to anticipate the lightning strikes and dodge, and she seemed to be having an easier time at it than she’d have thought.
Suddenly, Nightmare Moon tried another tactic: she hurled a flock of bats at Twilight. It was a mystery where those bats could’ve come from, but Fluttershy switched out, and immediately, the bats ceased to be corrupted. Fluttershy sent them back at Nightmare Moon, hoping that it would distract her---and it did! Nightmare Moon waved her hooves at the flock of bats, trying to recorrupt them, and that bought Twilight more time to keep smacking Nightmare Moon with arrows. Twilight noted that she was going to have to keep the pressure up if she was going to win this battle, but getting an edge of any kind, keeping Nightmare Moon from attacking her any way she could, would be helpful.
“Rarity, try a crystal prison!” Twilight shouted. Rarity hurled a gem at Nightmare Moon, and her chest and legs were encased in rock. Her head, however, was not, and she took that opportunity to hurl a dark ballista bolt at Twilight---much the same as how Shining Armor had done so. Twilight anticipated the attack, and she leaped over the spear, and did her best to keep firing arrows into Nightmare Moon. Nightmare Moon kept firing spears back, and Twilight had to keep leaping to avoid getting hit---and every time she did, she brought herself too high up to properly land a hit on her, and she could tell she was actually losing ground against the corruption. So she resolved not to try having Rarity use a crystal prison again.
Nightmare Moon finally broke out of the rock she was encased in, and began hurling lightning at Twilight again, exactly the way she had before. Twilight kept firing arrows at Nightmare Moon as quickly as she could, and she seemed to be making good headway against the corruption. But just as the corruption was nearly gone, Nightmare Moon switched tactics: she began firing wave after wave after wave of magic at Twilight, much the same as the magic Trixie and the Manticore had been using---only bigger. Jumping over them was difficult; Rainbow Dash had to switch out to properly dodge them. She tried sending a tornado at Nightmare Moon, but it had no effect.
Once the corruption had redone all the damage Twilight had cured, Nightmare Moon sent out another flock of bats. Fluttershy popped out and sent the bats back at her, and Twilight again began curing Luna.
Twilight tried to think---when little corruption is left, Nightmare Moon switches tactics. The lightning, she can handle, but those dark waves...? She needed some way to interrupt them, and whatever she did, it would have to be quick: if she didn’t keep the pressure on with her arrows, she’d lose ground again. Between dodges and arrows, she thought to herself: what are her options? The party cannon? Applejack’s earthquakes? ...The party cannon seemed like a safer option.
As the corruption was nearer and nearer to emptied, Twilight shouted, “Pinkie, get ready...!” Just as the first dark wave flew out at Twilight, she shouted, “Pinkie, party cannon!” Pinkie switched out and covered Nightmare Moon with fly strips. She began struggling against her bonds, and that stopped her from sending out dark waves. Twilight switched out and fired arrows as quickly as she could. The corruption seemed to disappear from Nightmare Moon, and her eyes stopped glowing red.
The core crackled and began seeping more corruption into Nightmare Moon, but while it was doing so, Nightmare Moon was completely motionless. Celestia apparently decided that it was worth the risk to try to use the Elements of Harmony on her at this point, because the next thing Twilight knew, her friends were all standing next to her. The energy of the Elements surged through her, and their rainbow-colored light slammed into Nightmare Moon and the core, destroying them both, and leaving a dazed Luna behind.
Immediately, the pounding against Shining Armor’s forcefield stopped; what had moments ago been Satallion’s army was now once again the royal guard and citizens of Canterlot. Slowly, applause and cheering began, and the sound of joy and victory filled the whole castle.
Twilight felt the adrenaline slowly flowing out of her system, and looked around. It hit her: she and her friends and her family had just saved the kingdom of Canterlot---she had done it! It was over! She looked over at her friends, and could tell from their faces that it was beginning to hit them, too, that they had won. She looked over at her family, and dove in for a hug with them. It was a tangled mess of hugs, nuzzles, kisses, and love, and it was one of the happiest moments of Twilight’s life.
Celestia walked up to Luna to see if she was all right. Luna looked up at her through tearful eyes. She moaned, just loud enough for Celestia and Twilight’s friends to hear it, “I’m so sorry, Tia!”
“Don’t be. None of this is your fault, Luna. There is nothing for me to forgive,” Celestia insisted.
“Yet...I am a threat to Equestria,” she whimpered. “I was once, and...and I fear I will be again! There is but one way to prevent Nightmare Moon from ever threatening you or your---our people!” Luna tapped her chest with her hoof. “Here is my heart. One thrust of your horn, sister, and Nightmare Moon dies forever!”
Celestia shook her head. There was love in her eyes, and sorrow that Luna was even thinking this way.
Luna pleaded, “I don’t want to become the Nightmare again! Please...you know when to stop being soft, and do what is necessary! I implore you---”
“Your heart is here,” Celestia insisted, tapping her own chest, “And my heart is there,” she added, tapping Luna’s chest. “Even if you become Nightmare Moon again, she won’t be able to keep her hold on you for long.” Celestia looked over at Twilight. “Look, sister. They are a family, and the love they share is a precious thing, and it is worth risking much for. Even if I had to face Nightmare Moon every year, it would be worth it to have you back.
“And no matter what happens, I believe with all my heart that you and I can and will share the same joy they do. Whatever else we may be, Luna---we’re a family.” Their eyes locked for a moment in silence; Luna was trying to decide whether to ask again for her sister to thrust her horn into her heart, and if so, how to ask it. Celestia sensed it, so she added, “I implore you, my sister: find the strength within you to believe that we can share this joy!”
“I...” Luna paused. “...I shall believe it, sister. And even when I do not believe it, I shall behave as though I do believe, for your sake. And...I hope that you are right...” She couldn’t say any more. Luna squeezed her eyes shut to try to stop the tears from flowing, got up, stood beside Celestia, and buried her face in Celestia’s neck. Celestia spread her wing over Luna’s back and gently kissed her sister. The crowd’s cheering crescendoed at this; they didn’t know that Luna was contemplating death---all they knew was that there was love between their beloved Princesses, and that was enough for them to cheer for.
Soon, the Spell of Unity kicked in, and only Twilight and Celestia were left in physical form. It took a long time for the applause of the crowd to die down; they were so glad to be free of the corruption’s influence, free to love each other, their nation, and their rulers.
But as the applause died down, Celestia decided now was the time to give them the sad, necessary reminder. With her booming voice, she shouted, “People of Canterlot! Hear your Princess!
“Our war against the demon who corrupted our fair city with dark magic...is not over! He still lives, and we are not yet safe. We have a plan to destroy him and subvert his plans for our fair nation. Return to your homes and rest; this has been a long day.”
Twilight finally stepped away from her family and asked Celestia, “W---what do we do now, Princess?”
“There are a number of things to get in order---I will hold council with the nobles and royal guard.” Celestia looked to one of the castle servants who was walking up to her, and said, “Have seven dinners prepared and sent to the audience chamber---I and the bearers of the Elements of Harmony will be eating them during the council. Even if it is irregular, it is what must be done.”“Yes, milady.”