Firelion:
Blackmail fantasies are one of my top 5 favorites.
For me, I usually fantasize about meeting an extreme feeder online (although I'm not aware of how far his desires go at the time) and agreeing to be his feedee.
We have lots of fat sexy talk and that gives him tons of evidence of my fetish and obsession, so he uses that to force me to gain weight.
At first I'm too terrified about anyone discovering my fetish, so I comply a little bit, fighting I can explain it as stress gain or something, but in my haze of fear at being discovered accidentally gain 100+ pounds and the feeder keeps going, wanting me to be at least 650.
I can't stop him or disobey him without all the stuff I sent being leaked, and at some point when I'm 500+ pounds, I realize that he has all the evidence he needs to show I wanted it and did it to myself, and there's no way out of his grasp.
Ughhh so hot.
Oh wow. That's a good one. Have you written any like that as I may try one myself. Incredibly hot.