What were the representatives of the plebeians in Rome called?

They were called tribunes and had considerable authority, including the ability to veto the acts of magistrates and even other tribunes. Perhaps even more significant, a tribune could use capital punishment against anyone who interfered with the performance of his duties. A tribune's power, however, was limited to the city of Rome and he had no clout at all beyond a mile of the city walls. The office was created shortly after the formation of the Roman Republic when the plebians revolted against the patrician class in what today might be called a general strike.