More ideas will come later on I'm sure, as I think of them. In the meantime, I'm very flexible with the details of any of these, and if any peak your interest please feel free to send me a PM!
The Apprentices (female needed)
Basic premise, two mages studying under an older, wizened master. The female would be slightly older than the male mage, and a little bossy and snobbish, despite the younger mage's greater skill. One day the master has to leave for a month or two, and leaves the female mage in charge. The male decides this as the perfect time to take some "revenge" on the other mage and subdues her, and thus begins their adventure of magically-charged sexual adventures.
The alchemist (female needed)
This roleplay would take place in a sort of, fallen london setting where your character, a young aspiring alchemist becomes my characters apprentice. Little does she know that she will be used to perform all sorts of sexual experiments, as my character slowly turns your character from an apprentice, to a slave. This roleplay will include all sorts of fun toys and fluids, though the exact details and specifics can be worked out individually.
The professor (female needed)
Your character, a college professor in her late 30s, has just got out of a rather nasty divorce, and on a whim, seduces and sleeps with one of students, which of course is my character. Afterwards my character would find some of your old bondage equipment, something you've always wanted to try but never got the chance to, and convinces your character to be his sex slave. Your character would be reluctant at first, but eventually submit completely, after a good amount of training and humiliation.
College antics (dom female needed only)
This story would be about two female college roommates, one of them is very extroverted and fun, while the other one is a lot quieter, she prefers to spend her time in the dorm while the other girl is out. What the outgoing girl doesn't know however, is everytime she leaves to go out, her roommate ties herself up and fantasizes about being taken and trained as a slave. This however, takes an unexpected turn when the extroverted girl comes back to the dorm with her boyfriend (my character), as they both find the introverted girl all tied up and helpless. Her roommate decides to take advantage of this, and with her boyfriend they begin to train her as a sex slave.
Playing with (hell)fire (2 female needed (can be played by 1-2 people))
This roleplay would involve two female magic practitioners in modern day, summoning forth an incubi in order to have him extract revenge on their enemies, as well as service the two girls. This backfires when the demon breaks free of their spell and captures the two, and decides to use them as his playtoys, making them performing humiliating sexual acts as he trains them, and (eventually) takes the two girls back into his own plane, to use them as sex slaves.