Glaaaaaaaaaaaaaaaaaaaaaaaaah
Fluttershy was having another sleepless night. Typical. The sleeping pills weren't working. Some nights, she was lucky to get so much as a few hours of sleep. Maybe it had something to do with the small pony-shaped beings that kept visiting her at night, pressing their faces against her window and waving at her. It was starting to get annoying.
Just last night, Fluttershy found herself trapped deep within the aortal bowels of a giant equine heart, locked in a duel to the death with a creature of liquid glass and broken pottery. As she stabbed the Beast in the Heart with a syringe, Fluttershy finally felt herself drifting off to sleep. What horrors and terrors awaited her tonight?
Ah, there they are. The Doll-Ponies were tapping at her window again. Grabbing her trusty spork, Fluttershy performed an ancient South Amareican rain dance to drive the creatures off in a cloud of acid-rain. Everypony knows Dolls are highly allergic to acid. Pretty, pretty, pretty acid. Why must you run away, acid? Why can't you stay and have a cup of tea with poor Fluttershy? Preferably chai, but she'd settle for black tea; none of that green drek.
1:00 AM. Still sleepless. Fluttershy decided to do the can-can. Can, can, can you do the can-can? Fluttershy can, can, can. She quickly got bored with that. She REALLY needed to figure out something to do. Maybe eat some fishsticks? Yeah, that sounded like a good idea. Fishsticks. Sticks of fish. No, not sticks of custard; that would just be wierd. Where was she? Oh yeah, food.
Oh Celestia... those fishsticks must have been rotten. Was that salmonella? Fluttershy was a bit rusty on her types of food poisoning. Reaching for a conveniently-placed bowl, she vomited. Her head spun as she stared into the depths of the pool of fish and pretty stomach acid. It almost looked like a little desert, the dunes of fishstick batter swirling in the translucent acidic winds. Fluttershy could swear she was standing there, gazing across the desert as a giant scorpion made entirely of hooves and eyes emerged from its burrow. Fluttershy cast a teleportation spell to escape before the Scorpion of Vecneigh could sting her.
Wait, hold on. Where did Fluttershy's horn come from? Last time she checked, she was a pegasus. Meh, she could worry about that later.
Then came the voices. Appearing through the walls, through the cracks in the darkness around her, glowing holes in the shadowy void, they whispered secrets of the universe into Fluttershy's brain as she tried to sleep, the whole of space converging into one point within her skull. Time has no meaning when all is one. Science. Science, I say.
Ugh. This was going nowhere. Typical, really. Maybe Fluttershy could write something? Or would that be right something? Write, right. Right, write. Right, right, write, right, wright, right, write. Half-formed thoughts and molten ideas coalesced in her brain, steaming, bubbling, seeking release. No, not THAT kind of release. Pervert.
She sat down to write. Her pen flowed across the paper both effortlessly and thoughtlessly as her brain spewed its contents into the paper, the ink acting as midwife to Fluttershy's broken thoughts and shattered dreams.
Satisfied, Fluttershy set down the pen and gazed down at her work. Her ribcage split open into a slavering, toothy maw, her intestines forming a massive slimy tongue that sucked the blood and bodily fluids from every living thing in her house, vomiting it back out through the bottoms of her hooves. Her right foreleg sprouted a set of five sickly fingers, each in turn growing a set of razor-sharp teeth. Her leg-arm detached itself from her shoulder and latched its many teeth onto her forehead. Fluttershy's eyes fell out; she watched helplessly as her own body betrayed itself, chewing through her skull and into her brain.
Darkness and shadows, secrets and lies reached up from the abyss, burrowing into Fluttershy's skin, shaking her very bones from the inside out. All around her she heard chittering creatures and moving shapes, forbidden colors stretching into the depths of nowhere. Screaming, Fluttershy reached for the lightswitch.
The light was like a badly-retouched photograph, flat and grainy, barely any color to be found. The wals resonated with a resounding thump-thump, which she swiftly realized was her very own heart, laying out on the dining table before her, still beating. She reached for the fork and knife, her eyes filled with manic glee, and began to consume the beating heart, piece by beating piece.
As she ate, Fluttershy's head began to swell; the more she gorged upon her own heart, the more her head grew, distorting into a grotesque mockery of itself, throbbing in agony, yet still she ate, unable to hold back the madness within and without. Soon she could no longer move except to glut herself upon the Heart, her head nearly filling up the room. Soon enough it burst through the walls and out into the cold, uncaring wind, chilling her to the bone as she finally ceased her consumption. Fluttershy closed her eyes and wept. Her tears formed a great river, flooding all of Ponyville in a torrent of misery, screaming ponies swept away in its wake. Fluttershy screamed, and Equestria trembled.
She had become a monster - a great, terrible, maniacal monster, devouring the heads of anypony that dared to cross her path, weeping all the while. She vomited forth a gout of rotting egg yolks, the transfigured remains of those she had consumed. All must die. All must die. All must die.
All must die. All must die. Thus spoke Fluttershy, the Beast in the Heart, as her journey reached its beginning, and its end, circling upon itself like the great serpent Ouroboros, devouring her own heart so that her head might live.
Realizing that something must be done, Fluttershy strove to break the cycle of madness and terror, sundering the great serpent and freeing herself from torment. She still fights that battle to this very day.