Prologue: A Recollection of Dread
It opened suddenly and without warning in the sky above Mount Saunter. If not for the loud bang that accompanied it, many ponies would have missed it entirely.
When I turned to find the source of the noise I was blinded by a white light - the only thing I could make out - but pegasi near the stratospheric layer came to report a ripple pattern, and described what looked like cracks in the air, itself.
Within minutes Princess Luna lead a squad of pegasi on a scouting detail of the phenomenon, while Princess Celestia remained in the castle, divvying up squads to soothe residents and tighten security. The Wonderbolts and other aerial teams had converged on Canterlot, drawn by the alarming event, and together we watched and waited for our princess to return with news.
As a soldier, you are trained to face the unknown. Monsters, mobs and panic - you've been exposed to it all. But when you find uncertainty, and even the seeds of fright in the eyes of your superiors, there is no greater fear. When Princess Luna returned, only able to confirm the pegasi's observations, I saw that uncertainty in her eyes. She nor Princess Celestia, as old and wise as they were, had the faintest idea of what loomed over Equestria.
And I wish that was the end of my recollection. I wish I could tell you the strange phenomenon was just that, and that the light had vanished as quickly as it had come. The reality, I'm afraid was far more grim - for the light was not a phenomenon of weather or known magic, but a portal. A portal, I'm sure, that'd one day be found in all of Equestria's historical records.
First was a dark shape, breaking free from the blinding light. With wing beats as powerful as any dragon, it cut through the sky with ease, circling the capitol like a scavenging vulture. What followed was a cry that chilled my blood and elicited screams throughout the city - an otherworldly sound that echoed to the farthest corners of the land.
Unprecedented mayhem ensued. No amount of effort from my fellow guards and I could have quelled the hysteria that overtook the ponies of Canterlot. The world lost all semblance of order, as ponies galloped every which way, toppling over tables, carts and each other in their search for shelter. Even the princesses were unable to regain control, seeking only to ensure that nopony got hurt in the chaos.
Shielding my eyes from the oppressive sun, I caught a clearer glimpse of what soared high above our heads. What I had perceived as a pair of wings and tail were actually a trio of clawed limbs, slicing through the air like lethal rakes. Pupil-less blue eyes shone even in the daylight, and horns as sharp as spears adorned its birdlike head. A thick grey plume rose from its neck, wispy and fluid in the wind like a cloud of smoke, and the black markings covering its underbelly seemed to glow a sickly red.
As shouts echoed out from terrified civilians, the creature's attention turned downwards, as if it had barely even noticed us before. It pivoted in mid-air to face the laying city below, and thereafter the air left my lungs - those grotesque claws gathered to a point, and an orb of black and red energy began to form.
Princess Luna's shrill voice called out, amplified by her own magic to reach the entire city.
"Everyone! Seek shelter, now!"
A horrid crimson blast erupted from the entity's chest, so fast that it struck the ground before my eyes could follow. Like a cruel magnifying glass tracking unsuspecting ants, it bathed an entire group of ponies in an opaque red curtain, then moved on to another, and another - chasing ponies down as they ran. Entire streets fell prey in just a few breaths, and the panic had broadened ten-fold. Our nightmare had escalated, and now there was no turning back.
Swarms of arrow-like projectiles shot from every trained unicorn horn in Canterlot, illuminating the sky in an all-out assault. As hundreds of lights collided with the avian threat, it warped the air with another cry, its movements growing spastic and agitated as it swerved around a second barrage. Soon our ears rang with those ghastly howls, and our forces scattered as red energy rained down once again.
I heard a command - I remember not from where - from amidst the chaos. But when I turned to locate the voice, I was met with cold faces, chiseled from stone. All around me, expressions of fright had been captured by the beast's magic, and the plaza had become a garden of statues. My legs shook - I had been paralyzed as well, not by magic but pure shock.
When the voice reached out again, louder this time, I felt a warmth soothe my chilled spine, and I regained control of my body. I gave a firm salute, for it was Princess Celestia who had called to me.
"Get under cover. Pull everypony you see inside with you, and let no one out until instructed otherwise by myself or another princess. Do you understand?"
"Yes, your majesty."
Though her face was hardened, her voice was firm and calm. Even so, she turned her attention to the sky, and behind her eyes I could see a restrained fury. She bit her lip, and I knew it best to speak only when spoken to.
"Stay vigilant and do not waver, or ponies may be missed."
"Understood, your highness."
The fluttering of feathers tinged my ears as she took to the air, soon vanishing from sight beyond the castle's distant towers.
And so my task began - I sought out each passerby I saw - stallion, mare and foal, alike, and ushered them indoors. We gathered in a nearby inn, vacant from the mayhem, and took shelter in its lobby. The muffled sounds of the conflict outside permeated the walls, and immediately I was besieged by frantic questions, none of which I could answer. From the inn's skylight we watched stray columns of red light fall like rain across the city, while blasts of magic illuminated the sky like fireworks. More than once I heard foals yelp in fright when the creature let out a cry, or struck a nearby structure with its powers.
It was a haunting thing. I did not fear it, but the more I watched it maneuver through the air, the more I was filled with an unsurmountable dread. My heart raced against my armor, my pours sprouted a cold sweat, and yet I couldn't explain why. I had survived being detained by changelings, thrown into chaos by the spirit, Discord, and survived neigh-armageddon brought on by Lord Tirek, but nothing in Equestria could compare to the creeping terror filling my mind.
"Mommy, where's the bad bird going?"
"...I-I'm not sure, sweetie, but you don't have to worry. We'll be safe in here."
I snapped back to attention. The creature, which had been striking at our troops just moments before was now withdrawing from battle, taking flight towards the rocky face of Mount Saunter. A few calls of excitement came from those around me as we watched the aerial force give chase, but I couldn't shake my lingering trepidation. Even when in full retreat the thing managed to be unnerving.
It slammed into the mountain above Canterlot, those massive wings gripping the jagged cliff like dug-in claws. Paying no attention to the advancing squad of pegasi, it heaved itself up onto a ledge, sending a small rock slide tumbling down the face in the process. Once perched it began lowering its head, curling and contorting its entire body, and by the time our forces reached it, the creature's wings and tail had formed a protective shell.
"Halt your attacks!"
An immense silence followed Luna's command, and the world grew still. All eyes watched, unblinking at the sudden stand-off - dozens of pegasi surrounding the mysterious creature, cornered on the cliff wall. Despite this advantage, not a movement was made from anywhere in the ranks. The unknown now stood before them, and it was surely more frightening than words could describe.
"The bird went into a cocoon, see mommy?"
"Yes, sweetie, I see. Let's just remain quiet for now, though, okay?"
I glanced at the mother and child behind me. Her resolve was admirable, perhaps even better than my own, but the subtle shakes in her voice were obvious. I was unable to offer comfort, to do anything besides stand over them as a shield from whatever monster had besieged our city, but in that duty, at least, I would not falter. Regardless the kind of threat I faced, I would stay by them, and that sentiment gave me strength. I suppose my parents did well to name me Stolid Stance.
Amidst my thoughts a tremor jolted the entire inn. We gazed up to find a field of energy spreading from all sides of the still cocoon, an even darker matter than what had been hurled at us, before. It spread quickly, obscuring not only the cocoon from view, but the sun, itself.
In the face of this, Princess Luna frantically ushered ponies away, signaling a full retreat of our own. Pegasi scattered like flies from the growing darkness, and from my limited view they vanished. Murmurs filled the room, but I remained rigid, for even breathing had become a labor for me. When I next heard screams - distant, but piercing - I strained my ears, searching for even a shred of what occurred beyond the inn's walls. All I could make out was a white noise of yells, unable to differentiate projected commands from cries of horror.
The once bright and blue sky above drowned in the face of this encroaching veil, and the madness in the room grew with the casting shadows. Even the castle's towers had been blurred by the force spreading ever closer to the ground. I could feel that same dread creeping on me again, stronger than ever, and I turned to face the cowering civilians behind me.
"Stay here, do not move! I am stepping outside for a moment, but I will not be far."
Charging the door, I dashed out into the empty street, scanning for signs of movement. Only the still victims of the beast awaited me, scattered about each street as far as I could see. The skies were void of ponies now too, thier screams gone along with them.
And so I drank in that unobstructed view, and my legs became numb. Blue slivers of sky laid beyond the city's borders, a fleeting hope against the black and red presence hanging over the entire capitol. Of those buildings overtaken I saw potted plants and other greenery rot away before my eyes, while the buildings themselves seemed to creak with age, their wooden frames dulling in color the longer they existed in that mist.
Instinctively I opened my mouth to shout a command, to tell those inside to flee to safety, but the words never came. The gravity of our situation had hit me, and I hadn't the means, nor the time, to explain it. I turned, and they could see the rising terror had infected my eyes as well.
"...mister guard sir, what's going to happen to us?"
The foal's mother gave me a look of desperation, but for some time I said nothing, my mouth too dry and my mind too shaken. Only when the sound of creaking wood approached from outside the inn did I find my voice.
"I...believe we may fall asleep, now."
My heart lurched in my chest at my own words.
"But we are together, and for now, that is what matters most. I will stay with you through all of this, you can count on that. Everyone...please brace yourselves."
Looks of bewilderment and fear crossed every face, all but the young foal's. While his mother gave way to sobbing, holding him closely to her, he watched me with a curious expression I couldn't quite place - calm yet full of sorrow, and hard like the face of a statue.
I glanced away to find the door frame overrun by a red cloud, and my vision was lost.
Author's Note
We interrupt your regularly scheduled fluff to bring you tales from the edge. 
The depths to which I enjoy FiM is only matched by my love for Pokemon. Specifically, I adore legendary Pokemon and the in-depth lore and mystery that surrounds them. I also love Dark-types. Add Ultra Wormholes from the latest games into the equation, and this kind of crossover was bound to happen.
This is my first published attempt at something quite contrary to my typical writing style, so I'm interested to see what people think.
As always, thanks for reading, and be sure to like and follow if you enjoyed it. 
