The Acting Prince/Princess is usually a Slytherin student of sixth or seventh year; but Tom Riddle claimed the title the youngest in the beginning of his fourth year. They have a number of duties; they will help their head of house with marking homework and tutoring if needed. They will supply the house with rules to follow that are for only them and not from the school rules. They will help with deciding punishments and running detentions if needed. Although if it is one of their rules broken instead of school rules, then they alone decide and deliver the punishment. They also help the Head-boy/girl and prefects with showing the first years around, and adjusting to Hogwarts. Their main role is keeping the students in line outside of the common room and maintaining the united front.