Creon is the brother of Jocasta, the wife of Oedipus, the king. He's accused by Oedipus of conspiring with Tiresias to take the crown from Oedipus. As a master of manipulation, Creon sounds convincing until the end of the play. It is then we know that his interest all along has been to become king. Creon does become king in the end when Jocasta kills herself and Oedipus blinds himself. Ironically, Creon becomes king through no actions of his own, but we see his true nature in the two plays that follow. Basically, Creon is used in Oedipus the King to set up the plots of the other two plays, which center around Creon as king.