Twilight Sparkle stood on the castle balcony, looking out across Ponyville towards the Everfree forest. She sighed, for this night, Equestria was at peace.
But not for long.
Twilight's gut clenched as she saw birds suddenly taking flight out of the Everfree forest, calling out in alarm. She readied her magic, channeling it to her horn.
Then the Everfree forest seemed to heave, and trees came crashing down, forest animals fleeing in panic. And it emerged.
It was a long, roughly rectangular shape, with slanted and curved angles that were concentrated around the top side of the "box". It rumbled up and out of the forest, dirt cascading off of its sides. Two low, blister-shaped things sat on top, each one having a long, hollowed-out cylinder protruding out. Two more, far longer cylinders projected straight up and out of the vehicle, pointed towards the sky.
The thing ground forward, heading towards Ponyville. Twilight gritted her teeth, snapped out her wings, and flew towards the monstrosity, determined that it should not reach the town.
A cluster of tubes swiveled, tracking Twilight. It did not appear to do anything else, yet Twilight felt incredible stabs of pain, felt herself coming apart...
"Enough", a voice boomed.
"Princess Luna? But how?" Twilight asked. She looked up, seeing Princess Luna fly down out of the sky. Only then did she realize that everything was calm and peaceful once more. She quickly whirled around, looking towards the Everfree forest.
There was nothing there. The forest stood quietly, undisturbed.
She turned around to look at Luna once more, who now stood on the balcony next to her. "I am the mistress of the night. That includes dreams, as you should well know", Luna stated.
Twilight, feeling sheepish, nodded her head in acknowledgement. "I know that. It's just that this seems so... real. Not like a dream at all." She gestured with her hoof towards the town of Ponyville, its residents sleeping peacefully.
"It is not merely a dream. It is a vision", a new voice declared from behind her. Turning around, Twilight saw Princess Celestia walking towards her, with Princess Cadence at her side.
"Princess Celestia? Cadance? How are you here?" Twilight asked. She turned towards Luna. "Did you bring them here?"
Luna nodded and replied, "In a sense. I did not bring them directly into your dream, but they have been having the same dream that you have just been experiencing."
Celestia spoke. "This is not a normal vision. This one is not of recently happened or past events."
Cadance added, "It is a vision of the future. A possible future, one that can be altered."
Twilight looked at all of them. "So how do we prevent this event from occurring?" she queried.
Celestia sighed. "We do not know. But keep your eyes open, Twilight, for one thing has been made clear. You and your friends will be instrumental to the solution to this."
Cadance looked at Twilight. "Keep your eyes open. Look for any disturbances, anything out of the ordinary."
Luna added, "We trust you, Twilight Sparkle. Ensure that this does not come to pass." Then all of them faded out of the dream, leaving Twilight alone once more.
Twilight turned, her hooves clopping against the floor. She stared out at the sight of Ponyville, its inhabitants blissfully unaware of the potential danger that lay ahead.
"I will defend you. Now and always", she whispered. Then she turned and walked out of the dream.