Maintaining the Evil Empire

The Evil Empire which dominates many eras in Fantasyland seems to have a talent for longevity while being pointlessly evil.Real-life evil regimes are usually toppled when their citizens can no longer bear living under their thumb, or when they manage to anger the citizens and governments of neighbouring countries with general evildoing.  Assuming that your evil empire isn't just evil in name only and actually rains misery down on its citizens, the  big question is how this presumably unpopular government maintains power (at least until the main character shows up to rally the ragtag band of underdog rebels).

If your plot requires a long-lived evil empire, you should explore the logistics of how they stay in power. A number of speculative fiction books actually focus on this theme-- 1984, Brave New World, and The Hunger Games being some of the best-known examples. But there are certainly many ways you can develop your evil rulers.  Just give it some good thought and you can have an opponent for your characters who is much harder to overcome than a generic Dark Lord.