The demon scam

For some reason you decide that you can trust this demon with the truth. "Well, actually..." you start with a little frown, "I and my sister came here from the mortal world by accident and we have to get back somehow."

The demon flinches and stares at you as if she doesn't belive what you're saying. "You're MORTALS..!?"

(Please remember the letter J.)

(What letter do you have?)