Devising a Plan

Luna and Hermoine really got into sucking the ghostly cocks, and the cocks just kept face fucking them until their jaws were sore, and they quit. "I guess they...don't...cum," said Luna.

"You know what...what would be fun?" asked Hermoine.

"What?"

"If we cast this spell on someone who did not know about the spell, and she finds herself face fucked by a ghost cock."

"Even better," said Luna, as she wiped some saliva from her lower lip. "According to this, there's a spell that gives someone the sensation of being fucked but there is nothing visible doing it. Imagine some girl sitting in class or in the great hall and suddenly she feels a cock in her pussy, ass, or mouth!"

"Oh my god, we have got to do that!"

"And we can control the size and length of the invisible cock," said Luna.

"Maybe we should try it out on us first?" asked Hermoine.