Mephisto Barto Dertov Reffert Lark Kucabara

Because some of the other demons did not like his kind personality they chased him away and stripped him off his status and powers. To regain them and to be able to return to his family he has to collect a certain amount of dark matter and at the beginning of the storyline he decided to do that by acting as a lawyer for sinners who were sent to hell. Source: bleachasylum.com