The setting sun spread an orange glow over the landscape, mounds of broken stone casting long shadows over the ruins of a long forgotten city. Celestia stood in what had once been a plaza; the stone beneath her hooves was still mostly flat, though long, jagged cracks ran through it. The alicorn took a deep breath and released it in a slow sigh as she stared at the steps that she could not bring herself to ascend.
They were in good condition, compared to everything else that she'd seen in that place; they were still recognizable. The blocks used to build them had been cut from the finest marble, a glorious stone. But glory fades. Now the gleaming white had faded to a dismal tan, and the precise edges rounded by gnawing time. Pieces that had been fitted so carefully were coming lose, and black gaps between them seemed to spread like rot across the construction.
Celestia closed her eyes. She remembered how they had been, so long ago, shining in the midday sun. There were no cracks, no spaces, no blackness, just a stairway crafted so expertly that it appeared to have been carved from a single piece of flawless marble. It rose from one plaza toward another, set higher on a hill. An unending stream of somber ponies broke, one or two at a time, from the noise and arguments and laughter of an open-air market to ascend while other ponies returned; coming or going, the ponies on the steps were silent.
She remembered how the whole city had been. To her left rose an ivory tower, impossibly high, dotted with golden balconies and stained-glass windows, and topped with a lavender spire. To her right roared the waterfall that freshened the water in a nearby pool before flowing on to drop to lower levels and, eventually, away entirely. Behind her loomed the reassuring mass of the largest and most splendid building in the city, and the one she was most familiar with. And ahead....
Celestia opened her eyes. It was all gone. To her left, a pile of rubble, irregular breaks and gently curving expanses all worn smooth by the elements. To her right, a puddle, silent and stagnant. Behind her, only memories. And ahead... her reason for coming, if only she had the will to face it.
The alicorn heard the sound of flapping wings and the dull clop of hooves on stone as a pony landed at her side. She waited, and the new arrival spoke, "Hello, sister."
"How did you find me here, Luna? Didn't I tell you not to come after me, when last we spoke?" Celestia said, her voice flat.
"Really? The first time we meet in over eight hundred years, and that's the first thing you say to me? I can't believe you, sometimes, sister," Luna said. She sighed and shook her head, then continued, "Are you truly surprised to see me here? I know what numbers hold significance for you, and my memory is as long as yours. Did you think that I would forget what happened a thousand years ago today?"
Celestia sat, and for the first time in centuries, she looked at her sister. "No. No, I suppose not. But I wish I could."
Luna met the other alicorn's gaze. She spoke with determination, "I used to be angry that you left, sister. So very angry. I had it all planned, the speech I'd give you when I could track you down. But it's gone. Just like this place. The years have worn it away. The anger. The speech. Now I just want to know: why did you abandon us?"
"I told you when I left. Ponies don't need me to rule anymore. You know that; you abdicated as well."
The younger sister stomped a hoof. "That's not a reason and you know it. I stuck around. I still have my observatory, my students. The heavens are still ours, and the ponies still appreciate that." Luna sighed as her anger faded, "It's not like they won't welcome you back. Ponies still know of you. They still love you. You're a hero. The summer sun celebration goes on as it always has. They even set up the stage and loop of gold, every year, hoping against hope that this celebration, after centuries of absence, will be the one you decide to attend. You're right when you say that our ponies don't need us. But they do want us. Come back with me. Celestia's School is still open, they even kept your office free! There's a pony that sits at the desk in your reception area doing nothing, in case you come back some day." Desperation entered the alicorn's voice, "Just walk in one morning, tell your secretary to bring you a newspaper and some coffee, and watch as half the staff ends up running around in a blind panic, trying to figure out what they're supposed to do. Wouldn't that be a grand prank, sister? Isn't that just your style? Please come back. Please."
Shadow had begun to creep across the alicorns as the sun disappeared behind a pile of rubble. Celestia shook her head. "I can't, little sister. I can't take on students anymore. It just brings back painful memories. I tried. You know I did, but none could compare to my first, and best, and most faithful personal student. Before her, I lectured ponies like a professor lectures her students. She was the first that I guided as a mother guides her daughter. No unicorn was able to replace her, to fill the gap in my heart. You know I tried. I can't stand to be reminded of her. Of how I lost her."
"And yet here you are, one thousand years after her death," the dark mare said.
"She deserves that much, at least."
"Why do you mourn her in this courtyard, then?"
Celestia kicked at the ground with a forehoof, "Because I can't bring myself to go any further, sister."
"Why not the library, then?" Luna asked, "I'm sure she would find that fitting."
"Where, Luna!?" Celestia shouted, her sudden fury taking her sister aback, "To where it used to be, when ponies still laughed and played and worked and studied in this place?" Her hoof pointed high above, to the side of a mountain where a few jagged remnants of worked marble clung tenaciously to the cliff. "Or to the pile of rubble it became after this empty city fell? Even without our subjects here, the reinforcement magic should have remained. You should have ensured it. I should have ensured it."
The white alicorn stood and turned, gazing at the mound of debris than had once been her castle. Her voice dropped, its anger replaced by bitterness, "You ask me to come back to the mortals, but I can't even return to my city. I only find a corpse when I try. It seems like just about everything I love turns into a corpse eventually. I ruled here for a thousand years as every pony I met grew old and suffered and died. I ruled here as Twilight Sparkle withered and weakened and died in my hooves. It seems that I rule here still; time simply ran out of ponies and turned the city into a corpse. Did it die of a fall or of my rule? Does it matter? It all just ages and rots and dies anyway. How can I live in a world that is crumbling around me, sister? Just smile and pretend that it's okay as I watch the buildings turn into boulders and the boulders break into pebbles and age grinds the pebbles into sand?"
"Who do you think you're talking to, Celestia? I know better than anypony. I see everything I build and every pony I meet crumbling. Do you think that abandoning it all to its fate and trying not to notice will solve anything? Wh-" Luna paused for a moment, then gasped, "You've been on the sun the whole time, haven't you?"
Her sister's silence was all the answer that Luna needed.
"Why would you banish yourself, sister? How could you stay? It's so lonely, away from everypony else."
"I stayed because it was better than watching Equestria die," Celestia stated.
Luna trotted around to stand in front of the other alicorn, glaring up at her. "Was it? Was it really? Did it make you happy?" Celestia looked away as the other mare asked again, "Are you happier now, sister?
"No."
"If you hate to see Equestria falling apart, then come back. You can't stop it, but you can work against it. When the buildings break, build more. When the trees die, sow new seeds. When your friends pass away.... Sister, you've got to make new friends," the dark-coated alicorn pleaded.
"The fate of Equestria does not rest on me making friends." Celestia replied.
"I know, sister. But your fate does. Twilight Sparkle would not have wanted you to abandon ponies, to abandon friendship, just because it can't last forever. She taught me how to enjoy what I had without worrying about when I would lose it."
The elder alicorn did not respond. Luna waited. She raised the moon as her sister finished lowering the sun, and darkness fell over the ruins. The cold night wind blew dust across the plaza as the sisters lost themselves in their respective thoughts.
Finally, the sovereign of the night spoke again, "She meant a lot to me, too, sister. More than we ever let you suspect. I didn't come here looking for you. I came because I come every year. And I'm going to climb those steps, whether you're ready to come with me or not."
Celestia looked at her sister with a new compassion as the other alicorn walked around and past her. She turned and caught up to Luna. Side by side, the sisters climbed the steps in silence. Above them was Canterlot's only graveyard, where they would pay their respects to the pony that had learned so much from each of them.