The above is an amazing fantasy, and mine is actually somewhat similar.
My ultimate fantasy is just that - pure fantasy, but here goes. Imagine undergoing a spell or ritual that makes you completely and utterly dependent on another man to achieve any sort of sexual pleasure. I imagine being taken deep into the woods along with 5 or 6 muscular and dominant men. I am stripped naked and kneel down as they form a circle around me. They chant in a strange, ancient language as I suck each of their cocks in turn. I am forced to worship each man's feet. As they chant, they all piss on me simultaneously to assert their dominance. I am forced up against a large tree as the first man approaches me from behind. I feel his hard cock pressing against my asshole. Before he begins to fuck me, I must say something like, "My body exists for the pleasure of real men, not my own." The first men then fucks me and shoots his seed into my ass. For the second man, I must lie on the ground with my legs up and repeat the same phrase before he fucks me and cums in me. I repeat the process in a different position for each man, with each man fucking me and shooting his load into me. It is forbidden for me to touch my own cock during the ritual. As the ritual progresses, I notice my cock becoming more soft and flaccid. After the 5th man cums in me, this symbolizes the completion of the ritual. I notice that despite the fact that I am horny beyond belief and that I have not cum, my cock remains completely flaccid. The ritual has made it so that the only time I can ever get hard or cum is when I have another man's dick in my ass. The process is irreversible, so from that day on, in order to cum or even get hard, I need to have another man fucking me.