Twilight and her friends are investigating the strange town of ponies without cutie marks, and when they talk with their leader, the devious mare tricks them, and proceeds to give them new talents. Kinky talents.

Heavily inspired by/based on an image from the artist bastianmage. The image in question can be found on derpibooru, and is NSFW.

Contains:
Transformations - rubber, semi-inanimate
Limb-removal (no gore, no pain)
Limited mind-control
Humiliation
Modularity
Non-con for the first chapter
Bondage, as a result of just about everything above.
Chapters 1 and 2: Female on female
Chapter 3: Male on female, female on female, harmless light abuse, consensual pretended hardcore-abuse
Chapter 4 - 6: Female on female.
Chapter 7: Female on female, pretend-abuse.
Chapter 8: Female on female.
Anthology 1: gore-less injuries and modular-oriented adventure, and male on female with exhibitionism.
The ending will be: a happy one, where the heroes win. Hard to believe? Just wait.

After some consideration, I've decided to include the non-consensual warning tag. Strictly speaking, very little in the story is non-consensual, but the situation as a whole is highly involuntary.

Thanks to The Great Derpsby for their help and encouragement.