I'm open to any rp ideas you have (really!) if you're not into that but if you are...
Here are the stakes of summoning me: if you lose, you become addicted to my cock. You can try to break my spell by defeating me in another match, but you have to skip your next turn when your desire is 70 or over and I use an action that includes a cock in the picture. If you win, I become bound to your will. I can try to break free by defeating you in another match, but three times in the game you get to choose my next action.
A failed attempt at escape comes with another curse devised by the victor. A second failed attempt, and the bond becomes... permanent.
I use hypnosis/bondage rules: you break free on a 5 or 6, otherwise you skip your turn.
Current mistress:
None.
Current harem:
Anastasia was temptingly close to making me hers, but she got careless and I gave her a nasty cock-addiction. She tried her luck again, but underestimated her addiction, and her will slipped farther away from her after I shattered it with a mind-breaking orgasm. No doubt she'll try again. [Edit] She did, and lost her will to me completely. My new harem bimbo is known as May.
Sweet Girl didn't know what she was getting into -- perhaps she was looking to lose. Lose she did, and now she has a new addiction. I expect she'll come back soon enough, if only to get another taste.
You can keep some notes on this character. You'll be the only one to be able to see this: