Inevitable. The prison's designer thought its borders were fixed from the moment it came into existence. Did that mean she only had to wait, and Nightmare Moon would be free to help the bats of Equestria anew?
Unless the ponies were right, and Princess Luna represented a horrifying danger to all other life. Of all the ponies to ever tell her that, she'd never considered there might be any reality to it until this moment.
Equestria's ruler would twist the truth to justify her own act of betrayal. Her loyal subjects were brainwashed by her words. But the subconscious of an ancient, dead pony? "That sounds like it would be good enough," she said. "All that time alone—do you think it might help the princess take back control? What do Outsiders even want?"
The unicorn shrugged his gray shoulder. He was clearly losing interest in her—the further she drifted from the original contents of this dream, the harder it was to speak with him. Clearly his vision didn't include a bat messenger asking about the finer details of spellcraft.
She was going to lose him if she kept talking for much longer. If that happened, the dream might expel her completely. Or maybe it wouldn't—the entire experience still felt bewildering and sideways.
"Can I see an example of your raw materials?" she prompted. "The stone you used to carve anchors. Maybe there's a flaw there we could improve."
The unicorn scoffed, but his horn glowed, and something levitated up from a distant shelf. He settled it down onto the ground in front of her with a heavy thump. A lump of pure marble, as close to flawless as any stone could be. Even the faded color of the dream didn't seem to reach it. "That was our first verification step, messenger. We used only the finest stone, carved by master masons, and inlaid with gold. You will find no fault with it."
Mira nodded. "Thank you, uh... Starswirl. For your patience with me. I hope you find the solution you're looking for."
He nodded absently, waving her off and looking back to his hooves. "So she says. Leave me to my work. My nightmare will be here soon. Let me prepare."
The castle rumbled with his pronouncement, like a great beast ready to spit Mira back up. Unfortunately for the dream, she couldn't let that happen.
I hope you don't mind if I take this from you, ghost.
Mira brought the stone with her, floating it through the air as though she were a unicorn. She didn't have a horn—but she didn't really need one. Just a little pressure to make the rock fly, and she could lead it away from the unicorn. Not far, just back into the hallway, where he wouldn't see what she was doing.
Could a dreamer even see something that was so obviously outside the context of their expectation? Maybe it would just collapse the instant she lifted her magical chisel.
Better not to find out. Besides—chiseling it would be too slow.
Mira already knew what the anchor was supposed to look like—she'd crafted its identical twin. Only the certainty of true matter could grant stability to the mercurial essence of the Dreaming.
Mira no longer remembered the precise reasons for her spell, for the runes she had chosen for each junction and their function. But she didn't have to remember, so long as she made this stone an exact duplicate.
Chunks of marble crumbled away piece by piece, as it approached the shape and size of her own anchor. As they did, the castle groaned overhead. Stone blocks tumbled and fell, and the ocean rose up in protest.
"I'm sorry, Starswirl," she whispered. "My friends need this dream more than you do."
Her runes came next, etched from the outside in as though by fiercely blowing winds rather than the carving chisel of a mason. Each face got its own lines of magical transmission that formed the bond between one world and another.
"Don't blink," Pixie urged, squealing up from her hooves. "This is the important part!"
Mira ground her teeth together, doing everything she could to ignore the kitten. She needed supreme, uninterrupted focus. If a single rune in her memory of the anchor was off, it wouldn't properly connect to the real one.
Last came the gold, filling the carved runes one at a time until each of them glittered.
"How are you doing that?" demanded a unicorn from behind her—Starswirl, watching from the doorway. "You aren't even a unicorn. Who taught you runecraft? And who—"
How is the memory of a dead dreamer acting so alive? Of course, the unicorn would be smart enough to recognize what she was doing if he was really here—but he wasn't. From his age, he had probably been dead longer than Kallisto.
"Luna. It's you, isn't it? Come here to... stop my work." His horn flashed, but the diffuse magic of his dream-self washed over Mira like a spray of mist. It tore off her saddlebags, shredded the robe, but left her intact underneath. Unless that was always his intention.
"You don't look like her."
What once was gray turned vibrant—Mira's anchor suddenly glittered, the gold radiant with the light of another world. Darker, but governed by concrete laws.
There were the cutie marks of sun and moon, little Alicorns flying sideways along the floor. Because it was supposed to be a wall.
"I'm not here to sabotage you, if it makes a difference. I'm here because Princess Celestia wants to exterminate every bat in Equestria. I'm here so we can live."
"Genocide," he whispered, barely audible. "Not her. The princess is better than that."
"Maybe she used to be." Mira bent down, scooping the kitten up onto her back. She had to be somewhere safe, considering what was happening to the ground at their feet.
The castle groaned and shifted, screaming in one last shout of vain protest. But the fragment of a dead dream floating here in the Astral Sea was far too feeble to resist her anchor. Light radiated from around it, restoring color as it passed. The material of this place began to rearrange—bricks lifted out of their spots, soaring away to form new walls. The wood from nearby shelves came apart into thousands of splinters, before reassembling into the trees they had come from.
"Not my work! You can't!"
Starswirl's horn flashed, and a heavy notebook appeared before him, so large he could only lift it with magic.
Somehow, the rearranging power of Mira's anchor passed over him, leaving him and the notebook the only patches of gray in the growing color. "You have no idea how important this is. Without this prison, Nightmare Moon will ravage the planet until it is unfit for life."
Not quite alive, then. You're still dreaming. The logic of this unconscious place mattered more than whatever real aspect she was communicating with. Ghost, fragment of the world beyond? Memory?
"Can you fly?" she asked, lifting up into the air. "We need to get onto the surface, or we'll get crushed in caves."
"Caves?"
She ignored the question, soaring past the unicorn into the workshop. As the anchor dismantled it, the wall exposed the open sky. Open sky that was itself a maelstrom of movement, chunks of rock and glass and twisted metal all moving of their own accord.
The fleeting substance of the Dreaming had already begun taking shape into the dream she'd placed in that anchor. That didn't guarantee it would make any attempt to preserve their lives in the process.
Mira scanned for an opening in the sea of material and found one. There on the far side, where a field of grass and trees already grew. There would be no more structures. She could shelter there while the world exploded and reassembled itself around her.
The boiling storm around the castle was gone now, replaced with a thick fog that obscured the ocean. Was the Diaspora out there somewhere, still struggling closer? Or had it already been crushed to pieces in the Astral Sea?
Too late for her to do anything now, except wait.
"I am sure you conceal nothing about your true self, bat," said a voice, calling through the maelstrom. Somehow, the dream unicorn could fly, or at least levitate himself there in a solid gray bubble. He remained protected inside it, a shadowy outline while the whole world was clear. "But I can't imagine who else could craft this magic."
"She taught me how," Mira said. "Or... that might not be the right way to explain it. Princess Luna did? Nightmare Moon. Someone showed me. Shared what they knew. I still don't know exactly how much I know. Sometimes it feels like I can do anything, but then there are holes."
As she spoke, what was once a fragment of Harmony had almost entirely reassembled itself into her vision for a new city.
It was not so grand as the ancient homeland of the dead, with its vast towers holding millions of bats. Mira was not so capable an engineer, nor could she build an anchor sturdy enough to sustain something so large. Besides, her own vision of where bats should live wasn't a perfect cage of glass and metal with flat black streets.
What she imagined was a better version of her home in the trees. What could Understory look like if they didn't live in constant fear of discovery and attack by Equestria? If they didn't have to hide in a cave, where would bats build?
A lot of it was still underground, of course. Surrounded by dense jungle, bats needed somewhere to go to get out of the sweltering heat and recover their strength. They needed a home that would protect them from the searing light of full day, even during noon on the longest months.
But there were buildings up here too. Massive trees, with wooden platforms and walkways between them. A great mountain high enough to be covered with snow, and a river leading down to a lake. Huge groves of mangos, bananas, papayas, plantains, and every other fruit Mira could remember.
Mira's vision of heaven didn't have magical boxes that stayed cold—but it didn't have winters either. The foals who lived here would not starve; they wouldn't have to run away from pursuing unicorns. The temple of the moon and its huge observatory could go right out in the open, at the center of the city.
"I expected warships," the unicorn said, almost conversationally. "You've invested some incredible effort here, but why? Anypony can build a city."
"Not in Equestria. The Golden Army hunts bats—we have to live with other ponies. If we go outside, they capture us, drag us back to be serfs to some noble or another. Unless they find us practicing dreamcraft. Then they kill everyone, no matter whether they knew the magic or not."
Mira landed on the grass just outside the temple. With her anchor in place, little trace of the dream's original function remained. No black and white, no ancient castle. Instead, the perfume of healthy jungle surrounded her, heavy and damp. She opened both wings reflexively, letting it wash over her. The occasional insect or jungle bird called out, gentle but ever present.
The unicorn landed just behind her, and his little glowing bubble faded. He still carried a notebook with him, clutching it close as though it were made of gold. So, some trace of the original dream remained, even after total transformation. "Then why here? Why my dream? You cannot tell me this was a coincidence. Oneiromancy is a difficult craft, and you are plainly expert in it."
Mira walked past him, to where the jungle trees ended on a towering cliff overlooking the sea. Beyond her island, a pocket of calm now appeared, where the ever-shifting currents of the Astral had no power to crush. A huge reef stretched away from the island, with an opening at the center wide enough for ships.
A huge metal vessel floated through that gap. Clouds of smoke rose from its single tower. A trail of bats led up from below, passing buckets between each other and dumping them overboard. Could that make a difference on a ship so large?
Maybe it was the intention to save the ship that mattered more than the amount of water they actually emptied.
Mira opened her wings, waving energetically to the bats far below. "They made it!"
A moth lifted off the deck, brown wings clear even at a great distance. They started yelling something, but Mira didn't hear it.
Something jerked her sideways, so harsh that her stomach twisted out from under her. A hoof from another place, tugging her out of the perfect dream against her will.
Nacht was suddenly standing over her. Mira blinked both eyes, fighting the delirium and confusion of sleep. "W-what are... Nacht?"
"The Golden Army!" he yelled, voice high and terrified. "They're already here!"