The ponies of the Crystal Empire were a bright and cheerful folk. Or at least, they tried really, really hard to be. They loved their Princess and they loved their Prince and they tried to believe that the noble pair could ward away all of the shadows. But deep in their hearts, the hurt and fear of their past could not be erased completely, and so bit by bit the shadows of the north grew stronger and the power of the Crystal Heart to keep them at bay slowly ebbed. The annual Crystal Fair renewed their protection, only for it to begin ebbing away anew.
The impermanence of their protection made it hard for the ponies to fully release their fears. And when the recent invasion of shadow creatures freshly reminded them of their past torments at the monsters' hands, they couldn't help but have troubled dreams and troubled thoughts.
But that was nothing compared with the burdens their new neighbors hid. Many of the Itinerant Kingdom had suffered such torments at the hooves of their fellow ponies in the past few years, and many of them had blood on their hooves from fighting back. Even those that didn't have blood on their hooves personally held a darker, more cynical view than they once had, and eagerly sided with the killers amongst them. After all they had been through, witnessed, and shared, every one of them believed that sometimes a bad pony just needed killing. They hid their thoughts under a veneer of sunshine and rainbows, with a mastery of duplicity taught to them by the changelings in their midst. For the most part they weren't suspicious of the crystal ponies: they had a soft spot for former mining slaves, as many of them had come from such circumstances, and assumed their innocence. Instead they pitied them for their presumed weakness, assuming they would crumple into submission again if the whip was raised against them again.
The Itinerants hid the darkness from their faces, from their voices, and their daily interactions. But they couldn't hide it from the shadows that lurked nearby. And so secretly, quietly, the balance of power shifted.
Garnet could barely stand when they left the restaurant. She was exhausted and a bit dizzy from hours of dancing, despite the food and rest breaks throughout the night. Her Prince had made good on his promise to show her off, and indeed by the end of the night there were clearly quite a few jealous looks at each of them. But despite the joy of it all, the crystal mare's body could only manage so much, and the Prince's tireless enthusiasm could only goad her on for so many 'one more' dances.
And so, the Prince happily left the restaurant on his hind hooves, carrying his marefriend in his forehooves surprisingly easily as he strolled down the street with a massive grin. "You're a Prince," Garnet pointed out, feeling almost drunk from the exhaustion, "you don't have to keep trying to impress me!"
"I know!" he said excitedly. "It is so freeing to be with one who knows that about me for once. Truly it is. And yet, my former guardian, Mr Muffin, would be aghast if I were to leave a lady in such a state without carrying her home. And if there is one thing Mr Muffin knew how to do well, it was treating the ladies right. Besides, it is no trouble for me. I am glad to have my hooves about you, whatever the reason."
Garnet snuggled against him with a pleased sigh. "It's too bad I'm so thoroughly exhausted. I'd love to show you a good time when we get home," she said suggestively.
"Such a beautiful sentiment from a beautiful mare, but you have already shown my a great time tonight. And we are both so young, there will be many, many opportunities to enjoy each other like that. Do not be in such a rush, beloved. I promise you it will be well worth the wait, and better still for having waited."
He skidded to a stop on his hind hooves as he rounded the last corner toward their house, remarkably managing to keep his balance despite the sudden maneuver. She started to question his action until her eyes focused on their surroundings. A black, oily looking mist blanketed the ground ahead of them, where the street dipped downward. It had almost risen to the level of their own feet, and seemed to be flowing into the windows of nearby houses. Garnet's home was on this street, far from the Itinerant District.
"No!" Garnet cried in alarm, clearly recognizing the mist. "Diamond!" she screamed out a moment later, calling her sister's name. That sister grumpily opened a top floor window, blearily looking in their direction before the sight of the mist called her to alarm as well. Soon everypony on the street was at their windows, clamoring in alarm.
Alex flew to Diamond's window, offering her a spot on his back, while the crystal pegasi nearby began carrying others to safety. Pegasi and griffons made their way south from the Itinerant District to lend their wings, calling out to everypony that could on the way to take flight and lend a hoof. "What is this mist?" Alex asked the Glitter sisters when he had a chance. "You seemed to recognize it."
"It's Nightmare Mist," Diamond informed him, "if it gets to you while you're sleeping, you may disappear, never to be seen again. And if you're awake when you touch it, you'll be plagued by nightmares for weeks. It shouldn't be able to get in here, not so soon after the Crystal Fair. Even without the Crystal Heart protecting us, the walls should be enough to keep it out. For it to have climbed this high without anyone noticing... "
The fliers worked tirelessly to evacuate everyone that could be evacuated, but the mist had already claimed several victims and guards that should have been watching the southern portions of the wall were missing, only blood stains and claw shaped gashes in the masonry were left behind to speak of their fate.
Despite the dire threat, a work force from the Itinerant Kingdom braved the mists to search the wall for holes, and worked quickly to patch the ones they found. After all, what were nightmares to the people who no longer slept? Before the dawn, they had assembled a series of pumps along the wall and used them to drain the remaining mist back over the walls, where it besieged them until the sun's light could burn it away.
Prince Shining Armor and Princess Cadance arrived as soon as they could. With their magic they reinforced the patched portions of the walls, and thanked the work crews for their efforts. I arrived belatedly, trying to give our hosts a stronger spot in the spotlight before I started giving orders out loud, adding guards to the walls and offering a place to stay in our district to anyone who didn't dare return to their own homes.
With the crisis handled, the Prince and Princess came to meet with me. "Are your people going to be alright?" he asked, concern obvious in his voice. "Some of them were in the mist an awfully long time doing heavy labor. I'm grateful for their help, but I worry what it may do to them."
"We've been warned to expect nightmares in the weeks ahead. We'll take what precautions we can, though perhaps it would be best to meet with Luna and enlist her aid in the matter. I have been putting it off, but in time I should meet with each of the Princesses. Personally, though, I'm more worried about what this portends. The mist didn't make those holes, nor dispatch your guards. This was just the opening salvo of something larger."
"If they are this bold so soon after the Crystal Fair we are in for a very difficult and dangerous year," Cadance agreed. "You promised to lend us your aid if battle should come. I trust you will be true to your word?"
"The Itinerant Kingdom will stand by your side. We all have something worth protecting here," I nodded. "You two are tired yet. Get some rest. We will watch the night, and meet with you in the morning."
"It's good to have dependable allies," Shining Armor said, though I could sense an undercurrent of doubt in his words. "We will see you in the morning."