The train ride from Ponyville to Canterlot took about an hour. Both ponies had made the trip numerous times before, so the view, though at times spectacular, held nothing exciting for either of them. Rarity used the down time to begin sketching some preliminary designs for Celestia’s dress. Her first sketch was meant to accent the shimmering of Celestia’s mane with a long flowing gown stitched together from different colors of satin, but then she thought better of it, deciding that Celestia often wore long flowing gowns; perhaps something a bit more slinky, or would that be too immodest for a ruler of Equestria? By the end of the trip Rarity had several sketches, none of which she felt were worthy of being showcased at the fashion event of the year. Twilight on the other hoof took the opportunity to get some reading done, managing to make it through a chapter of Quantum Magical Dynamics: Theory and Practice. Much to the surprise of both of them, there was a guard escort waiting at the train station when they disembarked.
“Does Princess Celestia usually send an escort to meet you at the train station?” Rarity asked.
“Well no,” Twilight admitted. “But I have my own castle now; maybe it’s just a formality, one of those things she has to do for visiting dignitaries?”
“You’re a dignitary now?” Rarity asked with a giggle. In response, Twilight shrugged sheepishly. “Well I certainly won’t complain about having some help,” Rarity said while smiling at the guards who were already beginning to load her copious amounts of luggage.
A short caravan ride later and the ponies found themselves at the entrance of Canterlot Castle as a different set of guards took their bags to the one of the many guest chambers housed within the Castle.
Twilight started to protest the help, “That really isn’t necessary, we can carry our own bags,” but she was politely rebuked by the guards who insisted that it was part of their job, nevermind that she was both a princess and the captain’s sister.
Their belongings attended to, Twilight and Rarity started toward the throne room. The throne room of Canterlot Castle was a monument to opulent elegance. Grand stained glass windows softly diffused a rainbow colored hue of light as it flooded into the chamber. The space itself was open, and high arched ceilings and convex walls gave the illusion that the room was bigger than its already considerable square footage. At the far end of the room, directly facing the entrance as well as the rest of the room, two thrones sat on an elevated platform. Princess Celestia sat on her throne, a literal gilded chair with a sun carved into the headpiece; upholstered with the softest of silk. Despite having been in the throne room and the presence of the Princess numerous times, Twilight and Rarity instinctively bowed as they approached, the layout of the room serving to place Celestia in a position of reverence to which bowing was the only appropriate response.
“Twilight, Rarity.” Celestia nodded giving them permission to rise. “Thank you both for coming so quickly.”
Rarity flashed what she hoped was a confident but relaxed smile. “Thank you for having us Princess Celestia, and may I say it’s an honor to be asked to help with the Gala in any way. Now, I have some preliminary questions I’d like to ask about what style you prefer before we go about picking out a color palette.”
A confused look ran across Celestia’s face before a more somber one took its place. “Would you both come with me to my private chambers?”
The two ponies wordlessly followed the Princess to the small room behind the throne, and when they arrived they were surprised to see a grim looking Luna waiting for them.
“Are either of you familiar with the legend of Apotheosis?” Celestia said, not wasting anytime with formalities.
Both ponies shook their head after a quick bow to Luna.
“Good. Much effort has gone into purging that particular story from the history books, and I hope you’ll understand why in a moment.” Celestia took a deep breath. “Before the rules of magic were established, there was a group of unicorns who began to explore the fringes of dark magic, areas that even warlocks fear to tread. In their ignorance they ended up creating a being of pure destruction, and they named him Apotheosis. But despite having created the being, they could not control him and it laid waste to entire cities leaving a trail of devastation in it’s wake as it ravaged Equestria.”
“That's awful,” Twilight said, before allowing Celestia to continue.
“Eventually a group of unicorns were able to lure the creature to the Ragorian mountain range, where, at great sacrifice, they buried him underneath the mountains, in the hopes that the sheer mass of the mountain would succeed in containing him.”
Luna snorted an audible hmph. “For a time they were right, though it is worth noting that their fiasco is one of the reasons the study of Magic is now tightly regulated throughout Equestria,” Luna added.
Celestia acknowledged her sister with a nod and continued. “Many hundreds of years ago Apotheosis began to stir. To meet in battle would have been folly, even for an entire battalion of unicorns, and so Star Swirl the Bearded devised a plan. He ventured deep into the mountains and cast a spell of oppressive darkness, surrounding the creature in a murk that could not be lifted. He then sealed the cave with a powerful force field, and locked the demon inside once again. Surrounded by all consuming darkness, Apotheosis believed his purpose to bring about the end of all things fulfilled and fell into a slumber. A small order of monks was set up to guard the cave. A few days ago they reported that the shield is failing.”
“Star Swirl cast a forcefield that lasted hundreds of years?” Twilight wondered out loud, desperately trying to run the calculations of how such a spell was even possible when taking into account entropy coefficients of magical energy.
“He was a skilled practitioner,” Celestia replied.
“Teach me the spell Star Swirl used and I’ll go to the cave and seal the entrance again,” Twilight said resolutely as Rarity stood meekly next to her, trying to figure out why she was hearing about this.
Celestia shook her head sadly. “Twilight, you are a very powerful young mare, and I have no doubt that in time you will rival Star Swirl. But Star Swirl cast those spells at the height of his power; even if you could learn such complicated spells that quickly, you could not hope to cast them at the strength necessary to replicate his work.”
Twilight remained undeterred, “What about Rainbow Power? We used it to defeat Tirek.”
Celestia shook her head again. “Rainbow Power is certainly powerful, but it comes from the Tree of Harmony, and thus must follow the same rules.”
“What rules?”
“The Elements of Harmony cannot be used as a weapon, only as a defense against evil.”
“A demon that threatens to destroy all of existence certainly sounds evil enough to warrant the use of Rainbow Power,” Rarity said, trying to make herself useful in a situation where she felt she had little to offer.
“Apotheosis isn't inherently evil,” Luna said.
“I don't understand. How can something whose sole purpose is the destruction and ruination of all existence NOT be inherently evil?” Rarity replied.
“Is a tornado evil? Or an earthquake? Is a desert that parches it's thirsty wicked, or an ocean that swallows the drowned unjust? Apotheosis is akin to these. It does not destroy out of cruelty or malice, only out of design. As such, regardless of the outcome of its actions, it is not evil.” Luna finished her explanation with a sad shake of her head, almost as though she wished her reasoning wasn’t true.
Twilight finished the thought process, “So Apotheosis can't be affected by the Elements and Rainbow Power.”
“Correct,” Celestia said, glowing ever so slightly with praise as she watched her former pupil work through another problem. “But while Rainbow Power cannot help us, we do have a plan, and it’s why we summoned both of you.” Celestia’s horn flared as she levitated a box about the size of a cake container from on top of a bookcase to her left. The box was carved from a single piece of ebony; ornate runes that Twilight could only vaguely recognize as Old Equestrian were carved across the top. It hummed with a sinister power as Celestia set it down in front of her. “This is the Nightmare Helm,” the princess of the sun said, opening the box. Inside was an unadorned light blue chamfron, it looked oddly familiar to both ponies.“It holds the key to great power, however I fear that it may come at a terrible cost.”
“Like the alicorn amulet?” Rarity offered, still trying to be helpful in a situation where she was woefully out of her depth.
“The Alicorn Amulet is a trinket!” Luna snapped. Seeing the look of fear on Twilight’s and Rarity’s faces as well as disapproval on the face of her sister she composed herself. “My apologies, this is…difficult for me to deal with. I had thought Nightmare Moon was behind me, to bring her back is a reminder of a past I have worked very hard to overcome.”
Twilight's face became a few shades paler and Rarity went completely still. “Nightmare Moon?” Twilight squeaked.
“Yes, Twilight. This helm contains the powers of Nightmare Moon, anypony who puts the helmet on is granted those powers. I called you both here because I believe that with this helm, Rarity is our best hope to save Equestria.”
“But we banished Nightmare moon,” Twilight protested.
Celestia nodded, “That's correct, you banished her. The elements cannot kill.”
Rarity’s eyes went wide as she looked at the helm with newfound fear. Like a puzzle she snapping into place she began to realize why Celestia had summoned her. Looking back toward Celestia she managed to squeak out a response. “You want me to assume Nightmare Moon’s power?”
Before Celestia could answer, Luna spoke up.“I wish to speak to Rarity alone.”
“Sister-”
“If you expect me to support this plan, you will grant me a few minutes alone with Rarity. I believe you and Twilight could use the time to catch up,” Luna said with a callousness that Twilight had never heard anypony use with Celestia.
Celestia nodded, first at her sister, then at Rarity and finally at Twilight, motioning for her to follow her out of the room.
The chamber now empty, save for the two ponies, Luna fixed Rarity with a fierce stare.
“Nightmare Moon has only one goal, to plunge Equestria into an endless night that she would rule. You must refuse my sister when she comes back. ”
“But if I say no, won’t Apo-whatever escape?”
“Both you and my sister suffer the delusion that in the absence of an alternative, any idea is a good one. This plan only trades one agent of doom for another.”
Rarity considered Luna’s objection, despite still not fully comprehending the forces at play. “Will you go with us? If anyone can help me resist Nightmare Moon’s power it’s you right?” The question came out as half plea half genuine curiosity.
“I dare not.”
“Is it because you’re scared?”
“No child, it’s is because I am not scared.” See a look of bewilderment on Rarity’s face Luna continued her explanation. “That kind of power is...intoxicating, even just being in the room with the helm I can hear it’s voice call out to me, and a part of me wants very badly to answer that call.” Luna’s eyes went glassy as she stared off into the distance. A moment later a shake of her head brought her back to the present. “I dare not go with you,” she whispered.
Rarity looked at the helm, then back at Luna, then she looked at the bookshelves filled with stories about gallant heroes who saved Equestria, that she was already in some of those books didn’t enter her thoughts. “Why me?”
“Nightmare Moon was created from my jealousy, her power was in part fueled by my darkness. But where I was greedy and selfish, you are the element of generosity, charitable and selfless. Celestia believes these qualities will allow you to use Nightmare Moon’s powers without succumbing to temptation as I did.”
“What happens if I can’t?”
“You don’t have to find out. Decline my sister's request, she cannot order you to do this.”
“What will it be like?” Rarity asked again.
“You don’t have to do this.” Luna insisted, her voice rising ever so slightly.
Rarity spoke softly, avoiding eye contact lest it appear as though she was challenging Luna. “Princess, it seems as though Equestria needs me. I’m sure if there was another way you would have proposed it already. I wouldn’t be a very good element bearer or a good citizen if I stood by while another pony risked their life in my stead. I’m going to do this, I’d like to know what I’m getting into.”
Luna sighed, the Element Bearers were not known for shrinking their responsibilities, it was one of the reasons they were chosen in the first place. “I suspect it is different for everypony. For me Nightmare Moon existed as a voice in my ear. She will lie to you, she will whisper what you want to hear and promise your deepest desires. When that fails she will tell awful truths to make you doubt everything you ever believed. No matter what she says you must resist whatever temptation she offers.”
“Well I'm partial to chocolate ice cream, but I think I can resist temptation,” Rarity said with a weak chuckle.
Luna glared at her. “Do not underestimate Nightmare Moon.” Rarity swallowed hard. “There is one more thing you should know. Nightmare Moon can only act through you. On her own she is powerless. If nothing else, remember that.”
While Luna and Rarity conversed in Celestia’s private chambers. Twilight and Celestia adjourned to a small meeting room nearby. One thing about Canterlot Castle was that it never lacked an empty room. Celestia flashed her horn and quickly set up some silencing wards. Satisfied that their conversation couldn’t be overheard she turned to Twilight only to have the young princess speak first.
“Do you really think I can teach Rarity enough about magic to reseal the gate, even if she does have Nightmare Moon’s power?”
“I have no doubt that under your tutelage Rarity can learn to control her new power. However, there is another reason I am asking you to go with her,” Celestia said solemnly.
Twilight looked up at her mentor with wide eyes, she recognized that tone, and it was never used to herald good news. “What is it?”
“Once the gate is re-sealed, Rarity must remove the Nightmare Helm, forsaking its power, if she does not…” Celestia paused, as though if she didn’t finish the thought that could negate its existence. “You will have to take it from her; its power is too great to let anypony wield.”
Twilight considered those words carefully and combined their meaning with the fear in Celestia’s voice; a terrible idea began to take shape. “Princess Celestia, I don’t know a lot about the Nightmare Helm but if it’s as powerful as you say it is, won’t forcibly taking it from her be dangerous?” Twilight asked, hoping that her conclusions were somehow wrong.
“Yes, it will be dangerous, that is why I want you to accompany her. Your magic should be powerful enough to remove it if she will not do so of her own accord."
"I'm not worried about me... I’m worried about Rarity. What will happen to her if I'm forced to take the helm from her?"
“It…it is unlikely she would survive the shock, that Luna did is no small miracle and largely due to the presence of the Elements,” Celestia said, destroying the fragile hope Twilight was hanging onto.
Twilight stood rooted to the ground. “No.” The word came out as a whisper.
“Twilight-”
“NO! You can’t ask me to do this, BECAUSE I WON’T DO IT!”
“Twilight-” Celestia tried again to get through to her protégé
“All my life I’ve done whatever you asked of me, well this is too much! There has to be another way. You can teach me the spell Star Swirl used, You could cast it yourself, we could send Apotheosis to ...somewhere! There has to be a solution that doesn’t put Rarity at risk!”
“You speak as though I have not already considered the alternatives. My power is connected to the sun, I cannot cast a spell of darkness. Luna’s power is connected to the moon, you may recall that the moon reflects the light from the sun, she cannot cast a spell of darkness anymore than I can. Even if we could send Apotheosis to another plane, it would be wrong to foster our problems on another universe.
“So instead you’re prepared to sacrifice my friend!” Twilight shot back with a glare.
“Twilight-”
But Twilight was unwilling to hear anything else. “You sit on your ivory throne, giving orders and platitudes about the ‘burdens of the crown’ but when it comes time to make actual sacrifices you do nothing!” Twilight knew the words weren’t true but she said them anyway; borne out of a selfish desire to hurt Celestia the same way she felt hurt by the circumstances.
For only the second time in their long relationship, Celestia found herself raising her voice at her former student. “I banished my only sister to the moon, who I loved no less than you love Rarity,” she fired back, letting her anger as well as her authority color her tone. “I would have rather cut off my horn then do that, but she would have plunged Equestria into endless night and I could not allow that to that happen.” Celestia softened her voice. “I am asking you to go with her, because you are the princess of friendship but more than that you are her friend. I chose you because I have faith that if she does succumb to temptation, you among all ponies can still reach her.” Celestia took a step toward Twilight and sat down, making sure to look her pupil in the eye. “Having power means having to make terrible choices, Twilight,” Celestia said, repeating the lesson she had tried to impress upon Twilight many times. “And now you have one to make. You can choose to deny my request and stay here. And if you do I will go travel to the cave with Rarity. But should you choose that path, and Rarity fails, you will have to live with the knowledge that you did not do everything in your power to try and save her. As cold as it may sound that is the reality you face.”
Twilight stood in front of her mentor trembling. “But what if I can’t get through to her? I’m not sure I can...take the helm from her,” Twilight said softly, unable bring herself to verbalize the consequences of what would happen if she was forced to turn her magic against her freind.
“I choose to have faith in you, and I choose to have faith that the Element of Generosity chose its bearer well, and I choose to have faith in friendship.”
“That wasn’t an answer.”
“Sometimes faith is the only answer we have Twilight. My faith lies with you,”
Twilight swallowed hard, “If I have to face Nightmare Moon, I won’t have the elements or Rainbow Power this time.”
“As long as Rarity is Nightmare Moon’s vessel her power will be…less…than when you faced her the first time. Rarity is not an alicorn, and don’t forget when you faced her the first time you were but a student. Now you are a Princess of Equestria. I pray that it does not come to it... but if it does, I have faith you will triumph.”
“That’s a lot of faith.”
“It has never been misplaced before,” Celestia said with the slightest hint of a smile.