It just had to be a Lamia
Fluttershy was a shy, squeamish, yellow pegasus, who often chewed her nails (much to Rarity's displeasure) when scared, and often had her muzzle in the ground when it came to big things.
That's why everyone was shocked to hear that she was going into the Everfree forest to find a plant that, once you made tea of it, would make one assertive. Fluttershy understood why they were nervous, the residents of ponyville didn't want another incident. Code 'Iron Will's Sidekick' they called it. Nonetheless, she proceeded into the forest, hoping to find the plant. The timid pegasus-humanoid saw a picture of the plant: Red vine with orange petals and old foresters tales say that it smelled of honey and strawberries, and so looked out for any unusual plant life or sweet smells.
For a large majority of the day she walked through the dense underbrush, stopping only occasionally to treat an injured manticore or to tell of a cockatrice for turning animals to stone, when finally something struck her nose. It was sweet smelling, so sweet that you could lose yourself in it, it was like honey and strawberries.
Wait. Honey and Strawberries!
The thought was enough to snap her out her stupor, allowing her to follow the scent to the plant she hoped she smelled rather than Zecora making another potion. Fluttershy's prayers were answered when she came across the red vine with orange petals. But Lady Luck wasn't on her side that day, because A) it was high in a tree, and heaven knows that Fluttershy is afraid of heights, B) a large timberwolf was sleeping under it and C) she forgot to pack something in to cut off a bit of the vine.
Silently she tiptoed past the sleeping timberwolf, sweating bullets all over her shirt out of nervousness, and began to climb the tree. When she got close to the plant, she quickly snapped it on a sharp branch that looked like as though it too snapped, and then quickly made her descent.
As she neared the bottom, her foot slipped, she fell and crashed right on top of the timberwolf. Not wasting a moment, she ran like as though her mane was on fire.
She ran for who knows how long, until she finally reached the cottage that is her home. Even with her legs burning and her lungs gasping for air, she continued to run until she got into her house. Fluttershy then quickly proceeded to bolting her door, before she finally passed out from exhaustion.
For hours she laid there, never being disturbed once (because her animals had evacuated in case of code 'Iron Will's Sidekick') until she finally woke up, she sat there for a minute until she stood up and made the tea.
As she looked at the caramel colored liquid she began to have second thoughts, before her mind began to produce images of things her friends will do that will look fun but, she too scared to do. So, in one gulp, she drank the tea. She sat there for a moment, nothing happening, until a great fire erupted in her legs. Pain, seeped its way into her stomach and throughout her body. Fluttershy clasped her head in her hands and opened her muzzle to scream. But no sound came out, it couldn't, the pain was too severe. Then she felt a tingly sensation wash down her legs. Looking down, Fluttershy could only gasp in horror at the sight of her legs fusing, tearing her cargo shorts. The shock, allied with the pain, caused her to go unconscious.
When Fluttershy woke up, she was greeted with a numb sensation in her legs, looking down again she was met with the sight of a snake's tail. Focusing hard, she slithered (if you could call waving her new tail 'slithering') over to the mirror she had, and 'stood' up. In the glass there was a yellow pegasus-humanoid with pink bangs, but were the shirt was supposed to be there was scales, in the formation that looked like as though they were clothing. The creature's belly was pink and the scale on it's shoulders looked like padding, and it's hands had tiny barbs on the palm, with the nails being extremely long and sharp. Protruding from it's mouth there was two long fangs, and it's eyes nothing more than ocean blue's with slits instead of pupils. Finally, its lower half of it's body was a snake's tail and, like the upper half's belly, it's belly was pink too.
This creature, it was her, it was Fluttershy.
It just had to be a Lamia
New powers New idea New victem
After having a mental breakdown (not only because of how she changed but also the fact that she remembered that it was irreversible) she sat there wondering.
What will my friends think? What can i do with this body? How will I make Twilight and the others join me?
As she wondered, her thoughts became more, dark, seductive, lustful, assertive. Then came a headache, flooding her mind with information on how to use her new powers: Hypnosis with her eyes, paralysis venom on her barbs, sleep venom in her teeth and how to convert others, into lamias, with all three.
Slithering across the room, she began to conjure up her plans. First, she will need to see if she can still fly with such a heavy tail, so that when she converts Rainbow Dash, the cyan pegasus doesn't flip out. Next she needs to find a way to lure all of her friends without them getting suspicious. Finally, she needs to find out what she can and can not eat. With her plan made up, Fluttershy slipped outside. During the times when she was passed out, it turned to night, perfectly concealing her actions as she tried to fly. After five attempts she managed to get her entire body ten feet into the air, before landing softly on her tail.
She then went inside, unaware that Angel and the other animals had witnessed what she had become, and waited for morning.
When Celestia's sun broke through the lamia's had she awoken. she didn't bother putting on clothes (her scales already looked like a shirt) and then grabbed her phone and dialed Rainbow Dash.
"Hello" came Rainbow's voice
"Hey Rainbow Dash can you come over to my cottage, I got a great surprise for you."
"Sure, be there in five" then the phone went dead.
Fluttershy then proceeded to close every curtain in her house and then hid on the ceiling. Then came the knocking. "Come in." she said.
The door opened and Rainbow Dash stepped through, not noticing a yellow tail close the door and locking it.
It was at that moment that Fluttershy dropped down from the ceiling, and before Rainbow Dash could react to the silhouette in the dim light, coils of snake wrapped around her. Then, her vision was instantly obscured int colours that almost immediately hypnotised her. Fluttershy then injected some of the paralysis venom into her prey so if she did break out of the gaze she would be unable to move. The lamia then bit down with her fangs on the cyan prey's neck, rendering her asleep from the venom in her teeth.
Looking at her soon to be lamia, she decided to act quickly because Rainbow Dash can wake up in moments, even if she was given enough anesthetics to tranquilize a herd of rhinos. Fluttershy opened her mouth, and swallowed Rainbow Dash whole. She then waited. After a few minutes, she began to feel pain in her abdomen. Then, a gap opened up and an egg, the size of a large box, came out, before the gap closed. The egg, cyan with rainbow stripes on the middle, sat there for a full minute before it started to hatch. Shell piece after shell piece until in its place, was Rainbow Dash with a lamia's tail.
