"What do you want in return? my soul or my first born?" Jason snorts almost derisively, he can't believe you're a demon, so he doesn't believe in the pact they're making either.

The long story short is that he met you at a lonely bar that was making waves in Gotham, because the people who sat with you had what they wanted most the next day. Jason had gone alone to investigate and now he was about to make a deal.