My dream scenario would he the sub, fixated, ideally in latex. She is allowed to talk and is relentlessly stimulated but is denied the orgasm over a long time so she gets so horny that she loses her shit.
Then, after maybe hours of begging to cum, she gets sensory deprived and a gas mask put over her head with a tube leading to a bottle filled with the mistresses piss so she has to smell it all the time and then fixate a hitachi or something similar to her pussy and let her cum over and over again and let her beg to stop it, but is denied the release for hours. You could also spice things up by shocking her nipples and pussy every 10 minutes for, say, an hour and then change it to shock every 5 minutes for an hour and then every 20 minutes for an hour so she loses every sense of time and space.