I did not initially intend on 'GM'ing this idea... but I did have something similar in mind. Granted, I think there'd only be 3 characters maximum... and due to the nature of the story (one of the characters having a great degree of control over the other), my role as a GM would be severely limited...
The three possible characters are;
The scientist's assistant
The experiment's subject/another assistant
So, departing from the original idea below a little bit- perhaps there is a love triangle... what with the assistants being in love with one another, or one assistant loving another who is in love with the sorcerer/scientist that transforms their adoring fan...
So I recently started playing a game called Path of Exile, and one of themes that appealed to me late in the game is the contrast of beauty and ugliness. One of the early bosses is a beautiful siren that slowly turned into a tentacle monster, the entire zone before her is sporadically peppered with illusions of her beautiful form beckoning you in.
But particularly towards the end, there are two temples occupied by opposing sides at war with one another. In the former, you fight through golden statues originally in alluring poses and what are basically animated tapestries (more terrifying then you think)
While in the second temple, it looks the same- with golden hallways and red carpets, but as you go deeper down, it is mostly inhabited by humans that have been experimented on and transformed into 'miscreations', until at the bottom level there's piles of bodies and literal pools of blood- some of the sickest metal-ist shit ever.
But I digress from the point, what I'm interesting in writing is;
A story about transformation, from something beautiful to something hideous. A basic I had took inspiration from that game, but here it is;
A sorcerer/ess begins to experiment on a male or female human... and with crazy magic, ends up slowly deforming the person over the course of the RP. The experimentee could be a lover or the crazy magic scientist is simply perverted, but sexual encounters continue unabated. Needless to say, neither character could be considered particularly sane at the onset of this story- and in fact towards the end there might be redemption for one... but probably not both.
What do you think?