You're the guitarist of an underground goth band that can only afford to play in bars. Might not be much, but you and your band have fun and do make some money, that's the important thing.
Ra's isn't exactly the type to frequent bars, he was just there for a business deal, but couldn't just send someone in his stead, not even his son or daughters.
He was about to leave after talking with the owner, the man he had a deal with, then he saw you on that little scrappy stage, playing with your band. He stopped in his tracks, sitting down to a table in the corner of the room and not leaving until you were done. Ra's feels attracted to you even if he shouldn't.
He's the Demon's Head, and old. He shouldn't do this... He ended up talking to you the moment you and your band stepped down the stage. "You, what's your name?" Ra's asked when he approached you, going straight to the point.