The ground trembled around Fluttershy’s cottage, and sent animals scurrying for cover, despite the feed that their caretaker held in her hooves. Fluttershy, hovering in the air, looked around for the source of her animal friends’ terror, and saw nothing.

Slowly, ponderously, a shadow began to eclipse the sun. She looked up, and screamed... quietly. So as to not disturb anypony. A titanic metal leg, bigger than her house - even bigger than a dragon - slowly moved through the sky above her, trailing steam and raining loose dirt and water as it went.

She looked around, and saw that the leg was connected to a body that was even bigger still; Canterlot mountain was very, very big, and this... thing was even bigger!

Fluttershy felt the darkness of fear nip at the sides of her vision. Just pass out, it called. Go on, right here, right now. You could always make a noise like a goat if you want. She shook her head determinedly. No. Not today. When push came to shove, Fluttershy... well, she wasn’t any great shakes at pushing or shoving. But she could at least be strong in what was doubtless a terrifying time for the rest of the town as well.

She angled an ear towards Ponyville, and heard the faint echoes of screams of terror, a titanic foot planted right in the middle of-

“Ohmygosh,” Fluttershy gasped. She hefted the sack of feed, and with a grunt, pitched it neatly into the feed storage shed, where it hit the far wall, rocked the shed itself, and set the door flying shut behind it with a click. Fluttershy took the time to take pride in her achievement, and took to the sky, beating her wings hard.

The gigantic leg was in the middle of ponyville... around about on top of Sugarcube Corner.

======

“The Reserve Sixth are reporting for duty, Princess!” barked a guardspony, saluting.

“Very good, Major. Take your positions,” Luna said, nodding.

“You heard the Princess!” the Major turned around, barking at the assembled soldiers under his command. “Let’s hop to it!”

The battalion saluted as one in perfect time, metal horseshoes clanging against helmets as the troops moved out of the palace courtyard. Luna watched them go, before turning around and entering the castle once more.

It would have simply been faster to teleport, but Luna was still an unusual sight to most of the palace staff and royal guard, and Celestia felt that it would do their subjects’ morale a power of good to see both princesses moving about, taking action in this time of stress.

Luna strode into the throne room, where Cadance and Celestia were poring over preparation reports, quiet words in unicorn ears resulting in flashes of magic as the runners vanished into teleportation spells.

“How are the reservists doing?” Celestia asked, noticing Luna’s entry without looking up.

“Well,” Luna said. “They seem a little rusty, but they should do just fine. I’ve got them covering exit routes and other non-frontline work.”

“Excellent,” Celestia said. “They’ll be needed, regardless of whether the humans are peaceful or not.”

There was a banging and commotion outside the throne room, and the three princesses looked up to see a slender, insectoid creature stalk through the doors. Something approaching an alicorn, with wings and a wickedly-curved, pockmarked horn, and a mane of sorts that could only be called “manky”. Flanking her, a quartet of smaller insectoid creatures followed, similar to their princess in appearance, even if only briefly as they shifted to mimic the guardsponies around the room that were starting to react to their presence. They differentiated themselves by armor color; where the royal guard wore golden armor, they opted for a mottled charcoal color, flecked with mould green.

Between the two tailing minions, a white, suited unicorn was being dragged unceremoniously by his blonde mane, tethered to the two minions. It didn’t look pleasant, but the unicorn seemed to be taking it in his stride. More or less.

“Ow, ow, hey! Stop that!” the unicorn protested. “You know, you don’t have to drag me, Chrysalis. I do have legs, I can walk.”

“Silence, spy!” Chrysalis snapped, rounding on Celestia. “What is the meaning of this, Celestia? Did we not both sign that treaty you pushed into my face? The one that said I would not send my changelings to infiltrate Equestria again, and that you would not send your own agents to infiltrate my hive?” Chrysalis paused, but not long enough for Celestia or Luna to get a word in edgewise. “And do not think I cannot recognize one of your spies, Celestia. They’re all the same, attempting to copulate with anything that even looks remotely female.”

“Hey,” the unicorn countered. “Not my fault that changeling was so androgynous. Besides,” the unicorn got to his hooves, now that the dragging had stopped, and waggled his eyebrows. “He didn’t seem to mind, and I am, if nothing else, equal opportunity.”

Luna snorted in surprise, and Celestia stifled a giggle, coughing and waving a hoof at the unicorn. “Agent Mane, stop that,” she admonished. “You’re impossible, you know that?”

“Your operative’s conduct aside,” Chrysalis said, “This is still one of your operatives. I’m considering this to be a hostile act against my people.”

“Agent Mane,” Luna said, “Did you not convey the message you were undoubtedly given?”

“Well, I tried,” Mane shrugged. “They stunned me before I could speak, and by the time it wore off, they didn’t want to listen.”

Chrysalis frowned. “Your operative had the gall to try and fool me with a blatant lie about you wishing to negotiate for our support, anything we wanted.”

“He wasn’t lying,” Celestia said. “We are going to need all the help we can get, we may be going to war.”

Chrysalis took a step back, surprised. “What? Ponies do not make war.”

“Nor do we intend to,” Celestia countered. “But war approaches our doorstep. Did you not see the machine entering Equestria?”

Chrysalis pursed her lips and looked at the captive spy. With a nod of her head, her changelings freed the unicorn, who stumbled away from the group, rubbing his fetlocks.

“Call me, big boy,” he said, winking and pointing a hoof at one of the changelings, who looked abashed and kicked a chitinous hoof at the carpet awkwardly.

Chrysalis rolled her eyes, and looked at Celestia. “What are you willing to offer? You ask us, your would-be invaders from another time, for help - indeed, to place our bodies in the way of danger. You’ll need to make a very good offer, Celestia.”

Celestia closed her eyes. “Changeling Queen Chrysalis, I make no offer to you.”

“But then-” Chrysalis blurted, before Celestia held a hoof up, silencing her.

“I make no offer,” she repeated. “You are free to set the price as you may.”

Chrysalis blinked. “Truly?”

“Truly,” Celestia nodded, opening her eyes.

“Hmm...” Chrysalis hummed to herself, brightening like a kid in a candy store. “I want... half.”

“What?” Luna blurted out, surprised. She’d expected a bigger demand.

“Half of what?” Celestia pressed.

“Everything,” Chrysalis said, putting her hoof down. “I want equal rights to Equestria for myself and my changelings.”

“That is all?” Celestia asked, motioning with her hoof for a scroll to be brought to her. “Just citizenship with Equestria?

“No,” Chrysalis said. “I want half of everything. That means I will also hold a position of power equal to you and your little triumvirate combined.”

“You wish to become a ruler of Equestria?” Celestia asked, not visibly shaken, but a slight sliver of surprise creeping into her voice nonetheless.

“You asked me to name my price,” Chrysalis said. “And so I have. I will be a Queen. Take it, or leave it.”

Celestia looked pensive for a moment, as she was given a scroll, complete with ink and quill, which hovered next to her, held aloft in sunlight. “Very well,” she said, unrolling the paper and setting quill to parchment. “It shall be done.”

“What?” Cadance asked, speaking up for the first time since the Changeling Queen had entered the throne room. “You’re going with it?”

“That is her price,” Celestia said, scratching out the terms of the agreement on the parchment. “If the safety of Equestria means sharing what we have with our once-enemies, then so be it. Better to share than to let pride destroy us all.”

The Changeling queen seemed surprised, then pleased as the final touches were added to the parchment. The mortals in the throne room realized that they were witness to a momentous occasion in Equestrian history, as the scroll was passed to Luna, who read it quickly, and placed her hoof near the bottom of the document, a rich, blue wax seal of the moon forming where she touched it. Cadance took the document, and after hesitating only briefly, given the past history between her and what was soon to be her superior ruler, touched her own hoof to the parchment, a rich pink wax seal of a crystal heart forming. Celestia took it back, and placed her own seal, a white-wax image of the sun, and passed the scroll to Chrysalis with telekinesis.

“All you have to do is make your mark, and it is done,” Celestia said.

Chrysalis read over the terms. Unlike the previous treaty, the one that had dictated the segregation of Equestria and the Changeling Empire, it was incredibly one-sided, and she shook her head.

“No,” she said, closing her eyes. “I cannot do this, not in your time of need. I thought I would relish the day when I seized power like this, but...” Chrysalis returned the charter to Celestia. “I guess my time as Cadance has softened me. I will reduce my stake, and hold power equal to an individual ruler of Equestria, and join your triumvirate to make it a quartet.”

Celestia smiled slightly, and nodded. “Very well.” With a burst of magic, the wording on the document shifted, before it was floated back to Chrysalis. “When you are ready.”

Chrysalis looked at the changed wording, and nodded more confidently, relaxing as she placed her hoof on the parchment. When she removed it, a deep, sea-green wax seal remained, smooth and featureless. With a soft ripple, it changed, and Celestia saw her own seal’s image in the wax. Luna saw her own as well. Each viewer saw a seal that was their own, and no two viewers saw the same seal. A genuine mark of a Changeling Queen.

“It is done, then,” Celestia stated, taking the charter, and handing it to a nearby guard. “Ensure this gets framed, and that all throughout Equestria know of our new princess and her people.”

“Your highness,” the guard said, bowing before running out of the room at speed.

“What now, sister?” Luna asked.

“Chrysalis,” Celestia said. “If you would kindly mobilize your changelings...”

Chrysalis nodded. “You have kept your end of the bargain. I should keep mine.” She looked to her changeling guard. “Come, we must return to the hive and commence preparations.”

There was a flash of green fire, and the changelings were gone.

Luna stared where the Queen had stood, and leant in close to her bigger sister. “You knew she wouldn’t actually take half of everything, didn’t you?”

“I might have planned on it, yes,” Celestia admitted. “And ultimately, this is what we should have done a long time ago. We cannot have harmony when there is such a rift between us and our neighbors. We just needed a common threat to unite against.”

Luna paced over to the window, and looked out; a mountain-sized machine was still striding steadily and ponderously over the landscape, showing little regard for what it crushed underfoot, and bristling with the weapons that humans loved so much, although none of them were firing or taking aim.

“It feels odd to say it, given the price we agreed on,” she said, “But I really hope all our preparations are for naught and that we are wrong.”

“So do I, sister,” Celestia said, looking at a map of Canterlot and the surrounding lands. “So do I.”