The sunset was torn asunder.
Bespoiling the medley of brilliant vermillion, crimson and orange, a rift began to manifest. Starting out as little more than a small pinprick of not-light, the void rippled and shimmered as it grew outward, a perfect circle of the blackest of blacks, darker than the deepest reaches of space. A gross bastardization, an outright refusal of all things harmonious and harmonic began to resonate within the air itself, a deep, thready thrum that supplanted within the royal alicorn sisters an overwhelming sense of dread.
“Sister-” Luna shouted out.
“I know, Luna. I know. Be ready.”
From the void, a figure began to emerge - tiny, given the great distance between the rift in the heavens and the top of the castle towers below. A pale white foreleg stepped through; then came the rest. The figure - tall as Celestia - descended from up above on skeletal wings. Indeed, the same could be said about the rest of the figure’s body: gleaming, white bones in a distinctly equine shape. Muted rays of the dying sun shone through the cracks and crevices in between the skeleton’s body. Atop its bare skull, two pointed, curved horns adorned either side. A dark, noncorporeal aura of red and black encompassed the nightmarish horror, swirling in between the figure itself. In its dead, receded eye sockets, two hateful pinpricks of blood red glowed with a feverish, maleficent intensity. With a frightening sense of purpose, it swooped down, bony wings beating against the cool air of the coming night. It hovered approximately ten meters above Celestia and Luna.
“At last...” the figure spoke, its voice a gravelly, grating bass that made the hairs on the back of Princess Luna’s neck stand on end. “At last. We, the Necrophant, hath arrived.”
With a tone of absolute, ineffable authority, Celestia raised her voice and addressed the creature. “And as before, we shall banish thee back to the vile realm from whence ye came.”
“Thou art not welcome in this world, Necrophant,” Luna added. “Thou bringeth naught but dismay, leaving total ruination in thy wake. We giveth unto thee, as we always have, but one chance - leave now, or face total annihilation, foul beast!”
The Necrophant only laughed in response - a horrid, wheezing cackle that sounded as dead as the maw from which it emerged. “And as we always have, dearest Princess Umbranox, Regent of the Night, we adamantly refuse. This world - this happy, innocent little world - it disgusts us so. Thy own charges, the ‘little ponies’ you claim to love and cherish so much, they knoweth not of the bliss, the all-encompassing pleasure that cometh with the Cantering Death. They knoweth nothing of true unity.”
“Your unity is death!” Celestia spat. “You take the most wonderful, sacred gift of all - life itself - and you twist it into a gross mockery of all things sane! My sister has the right of it, Necrophant. Thou art not welcome, and now thou shalt suffer.” That was all the warning the Princess gave.
With a brilliant flash of the purest golden light, the alicorn channeled a fearful volume of magic through her horn, feeling the raw magics coursing through every vein in her body, ruffling every feather in her graceful, alabaster wings. Her eyes were overcome with a blinding lambent glow, and she gasped sharply. Beside her, Princess Luna had already taken to the air, her own eyes in a similar state.
“We, the royal Alicorn Sisters of the free states of Equestria, do sentence thee to death for crimes against the kingdom. May the heavens take mercy upon thy pitiful soul!” Luna’s voice boomed out across the entire city of Canterlot, rattling nearby windows and causing a rain of detritus to fall from the armaments below. In a dazzling display of airborne agility and grace, the two regal sisters encircled one another in the air. Individual auras surrounded them - Celestia’s, a downy white; Luna’s, a deep, royal blue. The auras clashed together in a cacophonous boom, so loud that it echoed off of the very mountains that Canterlot itself was nestled within. The ethereal orbs of contrasting light meshed, flowing within themselves in a sort of yin-and-yang motion. A cyclone, of white and blue, emerged from the centre of the lambent display of raw magical power, coursing toward the Necrophant at a blistering pace. Yet, before the cyclone could fully surround the horror from another realm, it simply fell apart: vanished would be an accurate description. With a sudden outcry of anguish, Princess Celestia collapsed to the top of the spire below, landing hard on the smooth cobble.
“Sister!” Luna cried out, swooping down with great speed. Already, she could see the tell-tale markings of their one true fear - the only thing that has ever been known to harm the immortal
alicorns: a nameless, loathsome affliction which manifested in inky, jet-black streaks along an alicorn’s torso, slithering along the veins like some vile, nightmarish serpent. Celestia tried to stumble to her hooves, but slipped, falling once more to the cold surface beneath her.
“Damn it all,” she cursed under her breath, trying for a second time to collect herself. She managed to shakily gather the coordination it took to stand on her own free will. Celestia barred her younger, darker-coated sister from assisting her with a single, ruffled wing. “No, Lulu. He has bested me this time. You must flee.”
“No, I won’t! I won’t, do you hear me? Not again!”
“Thou misunderstand us, younger sister. That was not a request.” Using the very last bit of strength she could muster, Celestia encompassed Princess Luna in a shimmering, white light - and she then simply vanished.
Above, the creature cackled.
“Thou believeth that thy petty alicorn magics will saveth thine dearest sister? Amusing, Celestia. Thou art a constant source of entertainment for us, we must admit.”
“You-” Celestia began, spitting blood from her mouth. “You won’t be laughing when the Elements destroy thee, Necrophant. Even as I perish, I endure. You know this.”
“Spare us the dramatics, thou pitiful mortal thing. We have no desire for thy hollow threats.”
With that, the Necrophant enshrined itself and the Princess in a eerie, black not-light, and the two vanished as well.