You ask, "Who are you?"

"Who are you?"

She rolls his eyes. "Predictable. But fine, I'll humor you at least once." She smiles widely and holds his arms out in a grand manner, as if to show herself off. "I... Am sometimes called a 'Doppelganger'. Sometimes known as an 'Succubus'. But commonly, I'm something that your kind would recognize as-"

"A demon." Your eyes widen as you realize what she is. You recognize the words 'Doppelganger' and 'Incubus', though from what you've read you've always thought them to be very different creatures from one another. If there is one similarity between them, it would be that they are both known to bring misfortune onto humans. In short... They were both types of demons.

For a moment you wonder if she would be annoyed by the interruption, but instead she looks pleased. "Ah, looks like you're not as dim-witted as you seem. Looks like this might not take as long as I thought. That's right Casey, I am a demon. I was sealed behind this mirror for the longest time... But thanks to you, I will have the strength to return and wreck as much havoc as I please!"

Apparently you've messed up, big time. The King and Queen are fond of you, but you highly doubt they'd forgive you for unleashing a demon with the motive of wrecking havoc into their kingdom.

"Now don't look so worried. Don't you know that there are certain benefits to earning favors from a demon?"

"I've also heard that such 'favors' often involves giving up my life or soul."

"Hm, close but not quite. Luckily for you, I'm not the sort of demon that has any use for a lifeless corpse." Grinning, she kneels down and lifts your chin up to face her. "As a demon I could help you gather power. Riches beyond your wildest dreams. In which case, you will have to forge a contract with me.

"But... If you insist on playing a martyr, I can make a bet with you. If I lose, I will return to the mirror. If you lose, however, you will be sealed into the mirror instead and I will replace you in this world. I will simply change everyone's memory to make them believe that I was the original Casey Doe all along. Oh, don't worry your pretty little head about the gender difference. The human memory is a lot easier to manipulate than you can imagine."

"What would the terms of the contract be, if I want to make a deal with you?" You ask.

"Simple. You provide me with the source of my powers, which is 'lust' and I will grant every wish that is within my current ability to grant. If you neglect to provide your end of the bargain, however, off into the mirror you go."