Yes, they did have magical powers, but if Steve could convince them, maybe they could use their powers to return both himself and Carl back to normal.
"I ..." Steve began, then looked down at Carl. "Sorry, Carly, but I've got to tell them the truth."
Carly looked nervous.
"What are you talking about, Stephanie?" Agatha asked.
"My name is Steph-an ... ugh!" Steve said, in frustration. "I can't tell you my real name. Something is stopping me. Both me and Carly, actually. We're supposed to be women, not men. Damn it! It won't let me say the truth!"
Agatha stared wide-eyed, realizing what must have happened. "Are you saying that you both used to be men and that the Grellstone turned you both into women?"
Steve nodded "yes". "Can you change us back?" he asked her, hoping she'd do it. He didn't want to be a woman for the rest of his life.