Debauchery, of course

"What, who are you?" Petunia enquires.

"I am your master." Harry responds. "Now, you must be punished for your insolence, and actions in your previous life. Follow me, and no talking unless I instruct you to."

Petunia merely nodded and followed him to the Room of Requirement. They entered the room that had taken its sex dungeon form.

Harry directed Petunia to the bondage, tieing her up and placing a dildo in her pussy charmed to vibrate and edge her to orgasm, but not let her cum.

"You will stay here until I come back, once done you will apologise for your past actions and I will release you if you mean it, if not, I will leave you here for 2 days to have your mind break and rebuild you." Harry states.

Harry leaves the Room of Requirement, in search of new sex slaves.