Twilight Sparkle had only visited the Arcane Solar once in her life, but she had passed the heavily-guarded door leading to it many dozens of times. It was on the route between Celestia’s solar and the Grand Archives, and the insatiable bookworm had worn a groove into the flagstone floor traipsing between the two in her younger years. The first few times she passed the door, she had paused momentarily to wonder about its contents, and even after she had spent the night there, she had still marveled at the secrets the tower held, secrets nopony had ever really grasped. Over time, the door had become as the wall around it, silent, permanent, and essentially decorative, as nopony ever went in or came out. Even the guards who stood watch over the door seemed to treat the duty as punishment, though they maintained a sense of dignity and dedication all the same.
Today, the guards were shocked out of their ennui when Twilight walked up to the door, flanked by the two princesses. She smiled wanly at them as Celestia said, “Good evening, gentlecolts. We’d like to enter the solar, if you don’t mind.”
“Yes, princess!” they intoned together, bowing shallowly to the trio. Celestia inserted her horn into the lock in the middle of the door. The door glowed bright blue for an instant, and a dull click sounded from deep within. The entryway swung slowly inward of its own volition, revealing a distinctly unimpressive spiral staircase beyond. Twilight noticed the guards stealing curious glances as the three mares passed between them, confusion and moderate disappointment clearly written on their faces as they realized exactly what lay behind the door they were tasked to guard. Then the portal swung shut behind her and she was alone with the princesses again.
“Come along, Twilight,” Celestia said, starting up the staircase. Twilight followed a step or two behind, with Luna bringing up the rear. Lanterns adorning the walls of the stairwell flared to life as Celestia approached them, and extinguished just as suddenly as soon as Luna had passed. The party went through four more locked doors, each of which Celestia opened with a pulse of magic through her horn, generating a different color each time. Finally, they reached the top of the staircase, and approached one final door.
“That...was...a lot...of stairs,” Twilight panted, her legs shaking and sweat beading on her forehead.
“I’m sorry, Twilight,” Celestia said, “but you know how very specific magic must be. For the Solar to truly be the crux of all magic in the realm, it must be at the top of a tower with six doors and 192 steps. You understand.”
Twilight nodded, wiping a hoof across her forehead. “I understand. I just wish magic didn’t always need such big numbers...”
Celestia chuckled softly as she used her horn to unlock the final door with a flash of magenta magic. As the door swung open, Twilight felt a surge of magic burst forth from the room behind, washing over her and making every hair on her body stand on end. The unicorn felt her horn vibrating in tune with the arcane energies pouring out of the solar, filling her ears with the hiss of static interference instantly overwhelming her comparatively meager magical power. It was at once exhilarating and terrifying. Never before, not even in the presence of both princesses together, had Twilight ever felt so meek and impotent. Several seconds passed, each one longer than the previous, before the wave subsided to a slow, steady flow that ebbed past Twilight's trembling form, gentler now, but no less overwhelming. Celestia smiled faintly as she noticed Twilight's awestruck expression. "As I said, it is the focus of all magic in Equestria. It can be overwhelming if you are not prepared."
"I...I don't think I could ever be prepared for that..." Twilight said, her voice shuddering. "Why...why don't I remember it being so...powerful when I was younger?"
"You were but a filly, with substantial--but wildly uncontrolled--magical abilities. It is only because of your years of diligent practice, study, and advanced magical aptitude that you sense the raw power of this room at all. If you sensed it at all when you were younger, it would have been as a warm breeze, or a heaviness in the air. It would never have registered as it does to you now, as an overwhelming sense of power."
"I see," said Twilight, more out of reflex than actual understanding. Still vaguely nervous, she followed Celestia into the solar.
The room at the top of the tower was not particularly large, smaller even than Twilight's bedroom in the library back in Ponyville, but the ceiling towered several dozen hooves above her head. It was perfectly circular--a configuration magical energy often required--and the stones of the walls were polished perfectly smooth, with no seams or cracks. The floor was solid onyx flagstone dotted with glittering diamonds in patterns that Twilight instantly recognized as constellations. Even the sizes of the diamonds reflected the relative sizes of the stars they represented. There were no lanterns in the room, but a single glowing sphere hanging silently in the air near the ceiling, casting a pall of bluish light across the room and the occupants. In her hazy memories, Twilight recalled the room had had books and cushions for reclining on or sleeping, but now, she realized these must have been planted beforehoof by Celestia to invoke a sense of comfort and ease in the young filly. Tonight, the room was barren, without even a hint of dust to provide any indication of normalcy. The air hummed silently with magical energy that heated the room almost imperceptibly, and again Twilight could feel the sheer power of the solar hissing across her horn.
Despite all of this, however, the unicorn was stunned to find she felt...welcome. For all its awe-inspiring presence, the solar was not forboding in the least. She didn't feel overwhelmed as she had in the hall, nor meek and powerless as she had been fearing only moments before. The lilac mare relaxed, settling down on her hooves and letting her tail droop slightly. The static in her horn tickled, and she smiled in spite of herself. The light glistening on the floor was beautiful, shimmering in the diamonds and casting miniscule rainbows on the walls. Twilight glanced over at Celestia and saw the alicorn standing to her left smiling broadly, her eyes closed and her wings spread wide. The feathers ruffled ever so slightly in the ebbing magical flow, and the princess's ethereal mane and tail shimmered more than ever, the rainbows inside intense and magnificent. On her other side, Twilight saw Luna in a similar state of bliss, though her mouth was open slightly in a silly grin, and she leaned into the magic, letting the wafting energies flow through her royal blue mane. After a moment or two of this, Luna suddenly shook her head and recovered, glancing down at Twilight with a faint blush on her cheeks.
"My apologies, Twilight. The solar's energies are...unique..." she smiled again. "And wonderful."
"That they are, my dear sister," Celestia said. "That they are." Twilight looked back to see the ivory alicorn leaning forward to remove her crown and her necklace, and stepping out of her shimmering golden slippers. Luna was doing similarly on her other side, and once both princesses were nude--a state so rare that Twilight actually felt an improper thrill at the sight--they slid their adornments into a pile by the door. Reading Twilight's expression, Celestia explained, "It would be highly disrespectful to show any hubris in front of a deicorn. Cosmos may not be concerned with such petty concepts as pride, but it never hurts to show deference...and to remember one's place."
Twilight nodded. "But why not use magic to remove them?"
Luna smirked. "Try to manipulate my crown with your magic, Twilight." The unicorn raised an eyebrow at the alicorn, but the princess simply nodded at her trappings. Twilight did as she was instructed and was only moderately surprised to find that she couldn't seem to effort any magical effects at all. Her horn did not glow, or heat up as she was used to. She could not even feel the normal flow of arcane energy through it. All she could sense was the constant static interference from the energies within the solar.
The unicorn nodded. "I see...so no magic works in here?"
"No earthbound magic," Celestia confirmed, shaking her head. "Even Luna and I are overwhelmed by the forces here. Even our pegasus magic is inert. We couldn't fly if we wanted to."
"Amazing," Twilight breathed, trying again to evoke some response from her horn and receiving none.
"Prepare to be further amazed." The voice came from everywhere and nowhere, a statement Twilight would have dismissed as nonsensical before tonight. It came from all around her, from the air itself, from the walls, echoing and reverberating in her very bones, from inside her head, a soft gentle whisper in her ear, a cacophanous roar on the verge of painful. The voice was marvelous, at once powerful, awe-inspiring, and gentle, reassuring. It sounded like her father's proud support, her mother's loving wishes, like Celestia's approving commendation, and her friends' joyful laughter. It made her weak in the knees, but strong...confident. Despite the voice having no definite origin, Twilight found her eyes drawn back to the center of the room and was shocked to see what could only be the deicorn Cosmos standing in front of her.
He was tall. Easily twice as tall as Celestia, and broad, his inky black fur flowing over a sleek, perfectly symmetrical frame. The fur didn't seem to reflect light at all, absorbing it into the darkness and giving him the appearance of a silhouette against the wall behind him. His wings had no feathers, but flowed ethereally in the air above his back, like Celestia's mane. In them, Twilight could see stars flickering in constellations she had never seen before. His mane and tail were similar, flowing wildly around his head and flanks, the darkness of them studded with brilliant stars burning millions of miles away. His horn was long and sharp, with a point that Twilight could swore she saw cutting the very atmosphere around him as he moved, leaving tiny trails in the fabric of reality that sealed as quickly as they opened. His eyes were a pearlescent white, shimmering and iridescing in a myriad of colors, from blue to yellow, from red to green, and a thousand variations between. He wore a necklace much like Celestia and Luna, though his appeared to be hewn from massive blocks of diamond, with hundreds of brilliant facets enveloping a single large-cut onyx in the middle. His crown was likewise cut from diamond, rising to razor-sharp edges at the tops, and his hooves were ensconced in diamond as well. On either side of her Twilight saw out of the corner of her eye that both alicorns had dropped into deep, reverent bows, but the unicorn was unable to move, even to show the proper deference. Instead, she simply stood, her mouth hanging slightly open, staring at the magnificent being in front of her.
Several seconds of silence passed before the deicorn blinked, breaking the spell, and smiled, the corners of his lips barely visible against the black abyss of his fur. "My dear little ponies. How wonderful it is to see all of you again." The voice was still just as magnificent, just as powerful and awe-inspiring, but hearing it paired with the movements of the deicorn's mouth brought an additional sense of wonder and contentment to the little lavender pony in front of him.
Somehow, Celestia managed to speak. "Cosmos. It is wonderful to see you again, as well. Welcome back to the solar...and to our realm."
Cosmos smiled, the expression sending a wave of pleasure through Twilight's mind. "Thank you, Celestia. I do so love to visit you all here. It is remarkable, and not a little joyful, to see how you have progressed in my absence."
"We do our best to not need your intervention," Luna said, her voice requesting validation.
Cosmos nodded. "And you do well. It is my sincere hope--and yours as well, I suspect--that I need not return for many millennia after tonight."
"It is, your majesty," the princess of the night said.
"Time means little to me, but I imagine you would not wish to lose more than you must here tonight," the deicorn mused, glancing back at Twilight. "To that end, I will attempt to keep my visit brief. Twilight," he said, sending a thrill of terror and excitement down the unicorn's spine, "though this is the second time we have met, I imagine you do not remember the first."
Twilight swallowed hard several times through a dry throat before she managed to muster the ability to answer. "N-no, your m-majesty."
Cosmos chuckled softly, sending a shock of pleasure through Twilight's chest. "I remember it well. Time may have no meaning for me, but there exist certain remarkable ponies who stand out greater, more memorable than others. You are one such pony, my little Twilight."
"W-why is that, m-majesty?"
"My dear, call me Cosmos. It is the name your ancestors used when they called for my attention, it is the name they used when they sought my guidance, and it was the name they cursed when I abandoned them to their fate," he said matter-of-factly. "It is only right that you, of all ponies, should use it as well."
"Why me...C-Cosmos?" Twilight choked out, the name sounding thoroughly inadequate on her tongue.
Cosmos' eyes stayed focused on hers, even as the colors shifted and ebbed within them. "In all of this universe's history, there have only been--and will only ever be--three ponies who have seen my face. All three of these ponies have been graced with the greatest and most powerful gift I possess: the gift of immortality." The deicorn paused. "But I sense, as I had foreseen, that you are not entirely pleased with your endless life."
Twilight's face burned as she shuffled her hooves nervously on the diamond-studded floor. She suddenly felt foalish and stupid for being upset about being immortal. Of course it was a gift. A gift from a deity. How could she possibly be so idiotic as to resent such an incredible favor? She wanted desperately to lie, to say she loved it and to thank him profusely, if only to prevent him from being angry with her, but his piercing gaze carried the weight of eons, suggesting it would be unwise and fruitless to attempt to deceive him. "Um...well, you see...it's just..."
The deicorn smiled again, his eyes crinkling slightly at the edges. "Please speak freely, my little pony. You cannot disappoint me, nor anger me. I expect nothing from my children but that they be who I gave them the wisdom, intelligence, and freedom to be."
A warm wave of reassurance and sincerity washed over Twilight, instantly easing the tension in her chest. She took a deep breath and started again. "I just...I wish I'd had the chance to decide for myself. I wish I'd had the opportunity to grow old with my friends, to be...I don't know...to be..."
"Normal," Cosmos finished, nodding very slightly. "I understand well, dear Twilight. I may not know myself what it is to grow old and die, but I have watched many generations of ponies suffer the exquisite pain and joy of aging, the respect of the elder, the quiet comfort of the twilight years. It is one of the few gifts I had never foreseen my children missing when it was taken from them." Twilight wasn't sure what to say to this. Several seconds of silence passed before Cosmos spoke again. "I never force my will on my children. If old age is what you desire, I can provide you that opportunity."
Twilight's cheeks flushed again. Was she really about to refuse another gift from a deity? "Well, your majesty...it's just...I don't really want to get old now...I wanted to...you know, do it with my friends."
"I apologize, dear Twilight. You misunderstand. I mean to give you precisely that opportunity. Time is as nothing to me; I possess the ability--and the will--to return you to a time before your friends began to age without you, to let you experience the remainder of your life as a normal pony, unaware that I had ever interfered, or that I even exist. It is best, if you should choose this option, that you live as though we had never met, or you may have second thoughts about your decision, and your regrets may well taint what would otherwise be a truly remarkable experience."
"Y-you can?" Twilight said, her mouth falling open. "You could...you would do that? For me?"
Cosmos nodded. "Certainly. It is well within my power, and as I said, my children possess free will by my own design. You have been forced without your consent to live beyond when you should, and the pain you feel is my doing. If you desire, I can undo that. However," he continued, "there is an alternative, and it is one I wish you to consider as well."
Twilight blinked. "What alternative is that?"
"Celestia and Luna are two of my greatest children, and I am immensely proud of both of them. I am glad they have existed for millennia, as this world is greatly better off for their presence in it." He smiled broadly, and Twilight glanced over to see Celestia's face uncharacteristically flushed with pride. "Even Luna, who still blames herself cruelly for the effects of Discord's magic, is dear and wonderful to me, though I sense she still does not believe me when I say so."
"I...I do, your majesty, but I..." Luna faltered over her explanation, but it proved unnecessary.
"Fear not, dear Luna. I do not blame you. Someday you may understand and accept it, but you have many, many centuries ahead of you in which to do so. Regardless," he said, turning back to Twilight, "as I said, I grant only those ponies I find truly extraordinary the gift of immortality, but I wish to provide them even more. Celestia and Luna were the first recipients of my supreme baptism, and I would like you to be the third. To the best of my knowledge, you would also be the last."
Twilight's mind raced as she tried to piece together what the deicorn was offering. She heard Celestia and Luna both gasp in surprise, and she glanced over to see another uncharacteristic expression on Celestia's face: undisguised, unabashed joy. Confused, Twilight turned to see the same expression on Luna's face, though Luna's expression was, if possible, even more delighted. She puzzled for a few moments more over what Cosmos could be talking about before her eyes passed over Luna's long horn and wide, erect wings. It clicked.
"You," she started, shock rendering her nearly speechless, "you want...to make me...an alicorn?"
Cosmos nodded. "I would, very much. I foresee great things in your future, my little pony. You have done tremendous things with your life thus far. I would like to see you continue to surprise and enamor for many centuries to come, but I believe you can be even greater with the combined powers of an alicorn."
"I...I could...be like you?" Twilight said, looking at Celestia.
The alicorn nodded briskly. "And so much more," she said. "Equestria would benefit greatly from a third princess. You could be the deciding voice in critical affairs, you could be the voice of reason when our judgment is clouded...but more than that," she added, her eyes shining suddenly, "you could be our sister, and our friend, for all eternity."
"Twilight," Luna said from the other side, "I know you want to return to your old life, and to enjoy the experience you missed with your friends, but please...please consider his offer." Twilight looked to see Luna's eyes glistening as well. "We love you too, Twilight. We want you to stay with us forever, but...but we don't want you to do it if you don't want to. I..." she looked away for an instant, "I will be selfish and say I think you should remain..." The blue alicorn smiled weakly, a tear running down her cheek. "I...have to admit, I've enjoyed having a little sister..."
Twilight felt a lump rise painfully in her throat at the sight of Luna's tears. She looked down at her hooves to keep herself from saying yes just to stop the princess from crying, but was surprised to feel the heat of her own tears rising in the corners of her eyes. She closed them against the flood and tried to sort out her thoughts. "I...don't want to say no..."
"Twilight, please--" Luna started, but Cosmos interrupted her, his voice suddenly forceful, echoing fiercely off the walls.
"Luna, this decision is hers to make. Allow her time to consider."
"Yes, your majesty," the alicorn whispered.
Twilight continued, tears squeezing out from between her eyelids. "I don't want to say no. This is something I've dreamed about for years, just being an alicorn, being a princess...living here in the castle with Celestia and Luna...but I miss my friends so very much...and I would like to grow old with them." She opened her eyes, ignoring the tears sliding down her cheek and splashing on the mirrorlike floor. "But I still have friends," she continued, "friends who will miss me as much as I miss mine now. Spike, Celestia, Luna...and they will suffer for the rest of eternity for losing me." The unicorn looked up at Cosmos again. The deicorn's face was expressionless, a mask of neutrality. "If I went back, I would live out my life naturally, right? I wouldn't die early because of illness or injury or anything?"
Cosmos nodded. "Your life would play out precisely as it already has, but you would age and die normally. Specifically," he added, "you would die a mere two months after your beloved mate, happy, warm, and content in your bed at home, with your daughters and your dear friend Spike by your side. It is a good way to die."
Twilight smiled through her tears. "I don't suppose you would have anything to do with that, would you?"
The deicorn smiled faintly. "Perhaps."
Twilight looked back at the floor. Several minutes of tense silence passed with only the occasional fearful sniffle from Luna and the constant hissing of static in her horn interrupting the peace of the night. Finally, Twilight heaved a tremendous sigh and looked up again. Her eyes were dry and focused as she narrowed them at Cosmos.
"I've decided."