Think fast! How do you turn a plucky band of heroes into the underdogs?
With an Evil Empire of course!
Their enemy needs to be strong in the dimension they're not,
and nothing says "un-heroic but powerful" like an army of faceless minions in a castle with spikes on.
The evil empire is a literary manifestation of everything that your heroes typically aren't.
That is: organized, powerful in place, and with definitive leadership. Oh, and Evil.
Now this is useful because it serves as a foil to the heroes.
The contrast between them shows deeper aspects of the protagonists.
But there's another advantage to having an evil empire,
which is, you get to make it powerful in a dimension that your heroes just aren't equipped to fight.
You don't necessarily make them more powerful. Just differently powerful.
And an evil empire is just one instance of this trope.
In that case, organization and strength of numbers are unlikely to be assets to the heroes,
but this is just one instance of a larger trope used to make your villains actually threatening:
which is to make your villain dangerous to the hero in a way they can't defend against or fight.
I'll probably talk about this in more detail when I do a video on villains in general.
But for a quick discussion of one of the most classic examples of this, look at Lex Luthor.
It's obvious that his enemy, Superman, is stronger than him ...physically, in nearly every way.
Which is why Lex is only a threat because he has the smarts to actually do damage to him.
Now, in some instances, Lex is just written as using his intelligence
to make big scary monsters for Superman to fight, but that's not where he shines.
Lex is at his most dangerous to Superman when he turns public opinion against him,
and it doesn't sound like much,
but when Lex makes the people think that Superman can't be trusted, there's nothing he can do about it.
There's an example of that in the Justice League cartoon,
where Lex basically tricks Superman into destroying a low-income housing development.
Obviously, Superman had a reason to think he was doing the right thing,
but all Lex has to do is decry him as paranoid to the media, and there's nothing Superman can do about it.
Sure, Lex has done bad things in the past, but he's pulling a very convincing "changed man" act,
and now Superman looks like the irrational one for a reasonable bout of justified paranoia.
And it's not a problem Superman can punch, so there's no way for him to fight it.
Now, the "Strong Hero, Smart Villain" dichotomy is a very popular one,
but it obviously isn't the only one.
The one that's more common in, say, anime,
is the villain whose strength is in raw power, and the heroes, whose strength is in each other.
Alone, they can't oppose him, but when they work through all their emotional issues,
they compile the strength to take him down.
I'll talk about the power of friendship in another video (probably),
but there's a reason why those scenarios tend to include some kind of protagonist-y speech about how
real strength comes from fighting for something greater than yourself, or whatever,
and in the Evil Empire case the strength of the empire tends to be in numbers,
while that of the heroes tends to be something like guerrilla warfare and clever tactics,
or individual abilities, or whatever.
Now the evil empire is especially useful because, unlike the lone villain,
it seems monolithic and impossible to destroy.
There's only so intimidating one guy can be, but an empire? That's huge!
What can one guy - or rather, one group of misfit heroes - do against something like that?
Well, that's where the story tends to break down,
because the answer is usually beat up the boss and win the day
without regard to the actual consequences of a cultural collapse,
or acknowledging the fact that if you beat up the boss,
there's usually a line of succession set up to guarantee the empire persists even after the boss is taken down.
There's a reason why fantasy novels will often include a Rightful Heir,
who can step in and fill the power vacuum when the other good guys finish playing "Stomp the Tyrant".
Now, the problem here is when you draw on reality,
you end up with a situation that's less "Prince Caspian", and more "Game of Thrones".
When you break down an empire, you need another structure to take its place;
taking down the bad king and putting up a good one only works in stories,
but is unsustainable in reality.
You might end up with a benevolent dictator,
but give it a few generations, and the rulers will have forgotten why they bothered to be benevolent in the first place.
So in the absence of a "rightful heir" storyline,
a lot of the time the writer will just have the empire crumble when its leader is defeated.
But the problem is: when you overthrow a system, you need another one.
A cursory glance at a history textbook will tell you that the French Revolution led to 10 years of complete chaos
while they tried to sort out who should be in charge and how.
See, stuff like this is why evil empire stories tend to stop
before they have to address what happens in the aftermath.
But this is only a problem if the empire contains people we're supposed to care about.
If it's an empire subjugating people we like, we want to know they'll be okay after their government falls apart,
so those stories tend to invoke the 'rightful heir' thing
so we get the feeling they'll have some sort of support structure in place.
It's unlikely to last beyond the rightful heir's lifetime,
but that's the scale we care about, so it seems to suffice for the time being.
But if the empire is all evil, well: who cares, right?
Sauron only ruled the Orcs and some explicitly evil humans. Who cares if their government falls apart?
So as soon as his big eyeball tower explodes, all that's left to do is the cleanup in the actual places
we do care about.
And that kind of evil empire is both safer
and less believable to play with because it's got no grounding in reality.
It only exists for literary efficiency.
In the real world, there are no purely evil empires,
no situation where all collateral damage is justified because all the bystanders were also evil.
But fantasy and sci-fi love making entirely evil species that conquer other, non-evil empires in an easy-to-repair manner.
So when their empire falls, the subsidiary good-guy empires can go back to normal,
while the central bad guy empire collapses completely.
The only collateral in that case is the population and, hey, we already don't like 'em.
Now one thing that complicates all evil empire stories
is that your heroes just aren't going to be enough to take them down on their own.
There's that whole 'strength of numbers' problem again.
Even if the dramatic bit boils down to a 1-V-1 fight between the "Mainest Hero" and the "Big Bad Boss",
you need an army to fight an army.
There's a reason why your heroes will generally either join with or start a resistance movement,
or - failing that - strike up an alliance with a friendly empire,
and take care of their personal vendettas while the allied army does all the legwork.
Now the most important aspect of the evil empire is the evil emperor.
The complexities of the empire will be heavily determined by the nature of its dictator.
Now there are a few main kinds, so let's take a look at them. (This obviously isn't an exhaustive list,
but it is a broad categorization that I find works pretty well.)
The first kind is the emperor with an agenda.
This particular bad guy is notable in that he doesn't micromanage the workings of his empire.
Usually, he's content to pursue his own dark objectives, like evil sorcery, or living forever.
Sure, he's doing bad stuff,
but he doesn't tend to concern himself with the personal-scale workings of his empire.
He tends to be bad news for the heroes because they've managed to attract his attention somehow,
so he'll mobilize his elite mooks to take them down, and/or insist on getting them personal attention.
Defeating this guy is liable to have immediate good consequences,
because a lot of the time his control over his empire is at least somewhat supernatural.
But sometimes that means he's also the only thing holding the infrastructure together,
and without him the empire will "pull a Rome", and collapse under its own weight.
The second kind is the decadent bad guy.
He also doesn't tend to have much influence on the inner workings of his empire,
beyond the occasional gladiatorial arena -
mostly because there's likely to be 14 layers of bureaucracy between him and the actual civilians.
This emperor is a man-child.
He does what he wants, indulges whatever villainous ideas he has,
and basically just takes advantage of his absolute power.
He's very dangerous on a personal scale because he has no constraints and no sense of propriety,
and this is why he's generally not really in charge.
His bureaucracy is more likely to be made up of overly ambitious people
trying to manipulate the system for their own benefit,
but the emperor just tends toward some good old-fashioned chaotic evil.
Taking this guy down won't do anything to the structural integrity of the empire.
But putting a rightful heir in his place could possibly set things on the right course,
once they scrub out the bureaucracy a little.
The third kind is the maniac.
He's completely chaotic: ruling entirely through fear.
Do something wrong? He'll have you executed.
Look at him funny? He might have you executed!
This bad guy is bad news because he keeps his entire empire on edge at all times.
No slight is too small for this guy to take it out on you.
The good news is there is almost inevitably a rebellion brewing, with a well thought-out plan to assassinate him,
possibly even orchestrated by his own government.
The bad news is: this guy probably really likes making examples out of people,
so your heroes will probably have to stop at least one public execution.
Fortunately, there is no way killing this guy will make the people's situation any worse,
so feel free to have your characters throw out some justified regicide without worrying too much about its citizens.
Related to option three is option four: the Grumpy Usurper.
This is the guy who probably murdered his way up the line of succession,
and/or got the rightful heir - a character who's practically inevitable in the scenario -
exiled in order to make way for his ascension.
This guy is almost inevitably a terrible king, because he's too spiteful and petty to prioritize the big picture.
Worst comes to worst, he'll evolve into option three as a way of coping with his insecurities
about not being the proper heir or a proper ruler.
This guy's convenient because this story comes preloaded with the walking solution: the rightful heir.
Insert "Rightful Heir A" into "Throne B", and you're basically done.
Now as for evil empresses, that is: specifically female rulers -
because these options could all technically be unisex -
there are two, and they're basically "hot" and "cold".
"Cold" is the Ice Queen.
She's ruthless, heartless, and likely to order torture or execution without a second thought.
Now whether or not she's a good ruler is completely arbitrary.
Sometimes she restricts her cruelty to enemies of her empire,
sometimes it extends into a passionless ruthlessness towards her own people.
You're about 50/50 on that one.
"Hot" is basically the female variant of Option Three with an added dose of villainous perviness.
This one is gleefully cruel, and probably runs some sort of slave-based empire.
She also might try to make at least one of the heroes her consort
--oh, and either of these options could also be a "Daddy's Villain" if her father was similarly evil.
Each of these emperor archetypes come with their own matching empire
and personalized problems that arise when they're taken down.
So what kind of emperor you use is probably informed by what kind of heroes you're throwing at them.
But regardless, the sheer variety of bad guy emperors definitely show how
freaking common this trope is, and why.
There are so many stories that can only easily be told in the context of an evil empire.
If you want your heroes desperate and on the run, this is an easy way to do it;
if you want a daring and sneaky rescue mission, same deal.
If you're partial to exiled royalty, one of these probably sprang up in their absence.
Basically this trope recurs so often because it's useful,
and can be developed to an absurd degree of complexity if you want it to be.
So, yeah.