Dark Sun, The Scorched World of Athas
The sorcerer-kings rose to power long ago through unchecked arcane might. All of the remaining city-states, except Tyr, are ruled by the sorcerer-kings. Each of the sorcerer-kings is a powerful defiler, using magic to prolong his or her life to near-immortality.
Within the city-states, the sorcerer-kings are the absolute authorities, residing in their fortified palaces, rarely making public appearances without huge entourages.