A special potion ingredient

"Well, what is it you are looking to trade?" the shopkeeper asks nervously. He looks the two of you up and down, very conspicuously trying to see if you're hiding anything valuable under your dresses.

"Well, those aphrodisiac potions were junk, but I can get you a potent ingredient for you to make extremely potent ones," Catrya answers.

"Oh, you can get me something to make new aphrodisiac potions from?" the shopkeeper inquires.

"I can do better than that," Catrya retorts. "I can get you your ingredient right here for you if you like."

"What do you mean?" the shopkeeper quizzes, visibly confused to what your companion is referring.

"Let me demonstrate," Catrya begins, a smug grin appearing across her face. The wink she sends your way gives you a vague notion of the kind of "ingredient" she's referring to. Sure enough, with a wave of her hand her dress shimmers in a rainbow of magical light. As the magic flows over her body in iridescent waves, you can barely make out a subtle change happening underneath. After only a few seconds the magic fades, dispelling the illusion magic giving her the appearance of clothing. Though she still hides her skin tone and other inhuman features, she now presents her nude body in all its glory to the potion seller, including the churning ballsack sitting under her rapidly-stiffening cock.

The man's eyes go wide, his gaze fixed between Catrya's legs. With a slow nod he finally answers, "I think we can work something out."