Mephisto, having the bargain struck, decided in a special way to ensure the break-up. Sex is the key, but it's not enough for Peter to have a lot of sex. No, there had to be a better and more interesting way to do this. As he solved this, he smiled with a grin only a devil could.
A simple spell to summon the essence of lust and desire. The energy was now composed of the elements of sex, anyone fused with it would become irresistible to those he even slightly desired erotically. Second was a summons for the element of weakness to seduction and temptations, which would mix with Spider-man himself. Rendering him unable to say no, unable to stop, as women threw themselves on him. Or more precisely his cock.
"This will making him a loving sex god who is unable to resist any woman, allowing for massive amount of sex. But also making it soooo hard to commit to a relationship, even if I hadn't made Mary Jane Watson immune to these powers. She is the one women who is not magically compelled to him, her seduction actually guarded against by my spell.
A modification to remove all STD anyone he has sex with, but not the potential pregnancy. A touch here to make women more and more willing to have sex with Parker with each deeper erotic moment with him. A cloak of normality so no one can stop or even notice as odd all of the sex Parker is having, or who it is with.
The best part, with the sex spell, it makes it more and more likely Spider-man will let female villains go after orgasm. Makes him lead heroines to commit naughtier acts to be with him. Convince women in relationships to cheat and betray their lovers. A rise of wickedness. a pleasant side effect.
In the apartment of Peter Parker...
Peter woke up, exactly six months from when his wedding to Mary Jane Watson failed, mostly to his new problem. It seemed there wasn't a moment some hot and sexy lady was trying to have their way with him. Trying not being the word as they succeeded all of the time. He just couldn't explain it, but it happened. All. The. Time.
So as he prepared for the day, he was ready to...
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