The behavior of the Roman dictators-or Magister populi Praetor Maximus-changed over time, eventually turning into the ruthless, murdering heads of state we now think of (e.g., Sulla), but that's not how they started. The first of the Roman dictators may have been T. Lartius in 499 B.C. His master of the Horse was Sp. Cassius.
Consulship and Limited Government
After the Romans expelled their kings, they were well aware of the problems of letting a single man hold absolute power for life, so they created a split appointment with a set time period, one year. The split appointment was to the consulship. Since consuls could cancel each other out, it wasn't the most efficient type of government leadership when Rome was in a crisis caused by war, so the Romans developed a very temporary position that held absolute power in cases of national emergency.
Roman Dictators and Imperium
Roman dictators-the Senate-appointed men who held this special position-served for 6 months at a time or shorter, if the emergency took less time, with no co-dictator, but instead, a subordinate Master of the Horse (magister equitum). Unlike the consuls, Roman dictators didn't have to fear retribution at the end of their terms in office, so they were free to do what they wished, which was, hopefully, in the best interests of Rome. Roman dictators had imperium, like the consuls, and their lictores carried fasces with axes on either side of the city walls, instead of the usual fasces without axes within the city of Rome's pomoerium. UNRV notes that there were 12 lictors for dictators before Sulla and 24 from his day.
H.G. Liddell's A History of Rome From the Earliest Times to the Establishment of the Empire