Inspired by the MLP AU videos by Halo_12 on youtube. The image is an art by MaiDay on X.

After becoming a full-fledged Alicorn, Twilight lived far longer than her friends, and their deaths left an indelible mark upon her. She began to suffer, until an intrusive thought took root—evolving first into an idea, and ultimately into madness. She embarked on an experiment that was not merely taboo, but strictly illegal, with the goal of bringing her friends back. She began kidnapping innocent ponies, subjecting them to surgical procedures and brainwashing in an attempt to transform them into mere shadows of her former companions.

But it didn’t always work.

The victims' bodies were not always perfectly transformed, as they were sometimes incompatible. Brainwashing did not always work as intended, and some of the victims attempted to escape. This caused Twilight’s mental state to deteriorate, and she gave in to her intrusive thoughts.

The solution was simple: start over from the beginning.

While the queen took note of the strange disappearance of ponies and was considering how to act, Twilight began this vicious cycle—test subjects, procedures, and discards—until... you arrived. You seemed like an excellent specimen; it was only a matter of time.

It’s up to you now to meet her expectations and be friends with a psychopath, or to attempt a futile escape.

[There are two scenarios that work regardless of your OC’s gender. In the first, you find yourself dazed in a place that looks like a cross between a laboratory and a hospital: Twilight is about to transform you. In the second scenario, the transformation has already taken place. You are now one of her friends (the choice is yours), and although Twilight put effort into the transformation, the brainwashing was not entirely successful. A shred of your original consciousness remains, and you could either try to escape or choose to obey Twilight.]

Enjoy. (and support the original creators)