"So we might ... not even be on Earth," she stated. "I bet there's no way to find out for sure, is there?" Mercy realized then and there that she'd have to accept certain impossibilities and not pursue the unanswerable questions. It would probably drive her nuts at first, because she liked solid facts and she didn't do well with wild card variables.
"Why some spells and not others?" she pressed as she regarded him. Black, she decided, and it wasn't the light. His eyes really were black. That was kind of fascinating, and she very, very nearly asked if he was an alien (it made perfect sense, really; aliens could have magic) before she realized that could very easily be construed as rude, and she really didn't want to scare him off.
Though if she didn't stop staring like that, she was probably going to scare him anyway. Looking away in the 'what? I wasn't staring!' sort of way, she studied the barren landscape. That in and of itself was nearly enough to add significant weight to the 'not-Earth' argument, but ... places on Earth looked like this if they'd been hit with fire or bombs or nuclear explosions or something.