This stone, in particular, was the Carnal Amnesia Stone, which twisted wishes to become sexual or even erotic while also making the wisher forget that he or she had wished for anything and think that the new reality was normal.
For example, if Karyn simply wished to wear a dress, she might find herself in one of the most erotic dresses around "“ and she would believe this clothing to be completely normal for her.
Anyone else, though, who was within earshot of the wish would remember the previous reality and know that the wisher made a wish.