Nightmare Moon screamed her rage into the sky.

Her hooves slammed into the chalky white sand, kicking up dust, and her horn lit, firing a blast of teal energy into the sky. It dissipated long before it reached Equestria, hanging mockingly above her.

She screamed again. “Damn you, sister! You cannot imprison me here! Face me, you COWARD!” A crackle of energy blasted outward, turning moon rocks to dust all around her. When the smoke cleared, she was standing in a crater, that much further from her foe.

Further screaming accomplished nothing, and eventually she collapsed, tired, dusty, and alone.

“Doctor Clear Mind,” the courtier announced, as the pale gray unicorn approached the throne. He bowed deeply, before looking up at the Princess.

“What is your wish, Doctor?” Celestia asked, as if she didn’t already know.

“It has been three months since I last appeared here,” the Doctor began. “Your promised remedy has not materialized. The nightmares are getting worse. The most at-risk of my patients have begun to deteriorate in ways that may soon become irreversible. What is it that you intend to do about this?”

Celestia bowed her head, her expression somber. “I assure you that we are working on a solution as quickly as we can. The dream realm is not my forte, but I do understand your concerns—”

“You said this same thing months ago,” the Doctor snapped, sending a shocked gasp through the room at the interruption. “I do not want more empty promises. I want to know if you are any closer to a real solution.”

Celestia gritted her teeth. “Without my sister, I am afraid—”

“So go get your sister! Or do you expect us to suffer through this for a thousand years?”

“It is not that simple, Doctor,” Celestia responded, trying to maintain her composure. “I assure you, returning my sister to Equestria would have grave consequences indeed.”

“We do not need her in Equestria,” Doctor Mind mused. “We need her in the dream realm. Perhaps you could at least allow that?”

Celestia paused, her mouth suddenly a thin line. “Perhaps I could.”

It was lonely on the moon. Nightmare Moon had traversed its entire surface many times now, and found nothing but rock and dust. Her initial worry that she might starve had proven unfounded, however — she no longer needed to eat or sleep or even breathe. It wouldn’t have been much of a prison if it had killed her, she supposed.

Instead, all she had was time. Time to stew on what she had lost, how she had ended up here, what she could have done differently to avoid this fate. Lonely as she had been in Celestia’s shadow, at least she had had her guards and the dreams of ponies to keep her company. They had never been her friends, but even still, she missed them.

She had lost track of how long she had been trapped, but at least she could tell the days were passing by watching Equestria overhead. During the day, it vanished as the moon hid away, but at least at night she could look up and long for the home she had lost.

But tonight, something was different. Her horn tingled, and she took in a deep breath, for all that there was no air to breathe. It centered her, and the feeling of the magic around her was unmistakable. Her eyes widened, her horn lit, and suddenly the barren plain around her disappeared, and she was plunged into the starry expanse of the dream realm.

Bubbles of ponies’ dreams drifted past her, and she let out a giddy laugh, spinning around in delight. What had changed? She had tried so hard to break into the dream realm for weeks, but it had been closed to her since her banishment. But now it welcomed her back like a lover, and she settled into its embrace, for a moment too happy to contemplate anything else.

But it couldn’t last, and soon her anger came back. How dare Celestia take this from her, even for a tiny fraction of her banishment? She spun, and pulled up a bubble, and stepped inside.

The dream was dark, and an icy wind blew through the air. The Everfree Forest stretched out below her, the crumbled remains of the castle nestled in its center. Nightmare Moon hmphed, and with a wave of her hoof, the Elements of Harmony came to her, circling around her as they granted her their power. She spread her wings, blocking out the stars as she descended.

She landed softly on the balcony, staring down at the white shape huddled on the floor. “Get up,” she hissed. “I will not have my revenge sullied by your cowardice. This time, you will understand what it feels like to have the Elements betray you.”

Celestia slowly looked up, and tears streaked her face. She looked around, and then whispered, “It’s really you this time, isn’t it?”

Nightmare Moon scoffed. “Of course it’s me! How could you mistake any dream figment for the real thing? Now face me, and we will do this properly.”

Celestia shook her head. “I don’t want to fight you.”

Nightmare Moon growled. “Well, I want to fight you.” The Elements circled faster around her, humming with power, and her horn glowed as she channeled it into a rainbow-colored blast of energy down at her foe. Celestia would get the picture when she was forced to fight for her life.

But Celestia didn’t fight. She didn’t move at all. She watched the blast bear down on her, and she did nothing. It consumed her, and she screamed, and then there was nothing left but a smudge of ash.

Nightmare Moon glided down to what remained, brushing her hoof through it. “Disappointing,” she muttered, even as the dream faded.

“Please, listen to me,” Celestia begged, on her knees. “I granted you access to the dream realm—”

“SILENCE!” Nightmare Moon shouted, pressing her hoof deeper into Celestia’s neck. “You granted me NOTHING! The dream realm is mine to command, and you have no say over what I do with it! I am the master here, and if you will not fight me, you will be treated as the dog that you are.”

“Please, sister, our ponies are suffering—”

“Our ponies?” Nightmare Moon hissed. “Now they are our ponies, now that you fear my wrath? They were never mine when I was among you, always yours. You were their shining, precious light—” her voice could barely contain her spite, “—and I nothing but your shadow. You may have trapped my physical body on the moon, but I can at least make you suffer in your nightmares for a thousand years. That should be punishment enough for your hubris.”

Celestia barely shook her head, the largest movement she could make with her muzzle pressed into the stone floor. “Perhaps I deserve as much for my neglect,” she murmured. “But our… my little ponies do not. They are overrun by nightmares in your absence. You can help them, as you once did.”

Nightmare Moon let out a huff. “And why would I do that?”

“Because you care for them as much as I do, or you would not have been so consumed by their rejection.”

Nightmare Moon’s eyes widened, and she stepped away, only to give Celestia a swift kick in the ribs. “Lies! I care only to make you suffer as I have. Your subjects mean nothing to me.”

Celestia slowly struggled to her hooves, staring at Nightmare Moon with sad eyes. “I was afraid you would say that. Please, sister. There must be some part of you that still wishes for their happiness. They do not—”

“What do you know?” Nightmare Moon hissed. “If you had any idea what I wished—any idea what made me happy—” She growled. “Argh! I will not be tricked into listening to you again. You will suffer, as I did.” She raised her head, and sent a blast of magic at Celestia. It charred her fur and blackened her horn, and she screamed in pain once more. This beam did not destroy her. Instead it left her smoking on the ground, struggling to breathe.

“I am sorry, sister,” Celestia gasped. “I am so, so sorry.” Her horn crackled to life, and suddenly the dream became murky, as if flooded with water. Colors faded and ran together, and their surroundings slowly dissolved.

“What?” Nightmare Moon hissed. “No! Come back here, I am not done with you!” She leapt forward, but there was no longer a ground to leap from or distance to cover. She tried to pull the dream together, to force it to her whims, but it ignored her.

“Luna… I hope you will forgive me someday,” Celestia whispered, her body whole again, standing with her in the infinite dreamscape. “I never meant for you to become this.”

The starry void of the dream realm swirled around them, before the dreams clustered around Celestia and began to fade. “NO!” Nightmare Moon screamed, clawing at the bubbles, but they evaded her before the entire dreamscape shattered, and she was on the moon once more. “NO! You cannot do this to me! Bring back my dreams!” She lit her horn, searching desperately for the dream realm, but it was already gone, locked beyond her reach. “NO!”

Luna collapsed to the ground, heedless of the dust, sobbing. “Please. Please bring them back. I’m sorry. I didn’t understand.” She slowly curled up, burying her head in her wings. “Don’t leave me here.”

No one answered her. The moon was silent, dull, and empty, and she was alone.