Nowadays, a game is pretty much required to have a solid replay value to be well received. Having multiple difficulty levels is a simple way to prolong the life of the game, but then Numerical Hard
is to be avoided at all costs. So a common way of increasing difficulty is to put the player against tough mooks earlier and more frequently in the game.
And then there are games who not only do that, but create news enemies that you will meet only
in difficulties above normal, thus surprising players who thought they had already fought everything. Of course, expect these enemies to be Demonic Spiders
or Boss in Mook Clothing
Some games make it so that some tough enemies don't appear in diffculties below normal, but then it's more a case of Easy-Mode Mockery
Compare Level Scaling
, which has a similar effect but minus the difficulty setting angle. Also compare Replacement Mooks
, a sort of narrative equivalent.
- A lot of named aces in Ace Combat Zero: The Belkan War only appear on Hard, Expert, and Ace difficulties.
- The Game Boy version of Daffy Duck: The Marvin Missions had a special series of hard levels that you can play though if you beat the first screen on a Speed Run. These levels feature a few enemies that don't appear in a normal playthrough.
- In the original The Legend of Zelda game, Red Bubbles (which take away your sword permanently if they hit you) only appear in the Second Quest (that game's version of a Hard difficulty).
- In Lollipop Chainsaw, there are named zombies you need to slay to complete an album, and some of them only appear on harder difficulties: 
- Ninja Gaiden Black, and by extension Sigma, has the Ryu clones, mini-bosses who appear unexpectedly where you fought common enemies in Normal mode. Then in Very Hard, you meet a new type of Black Spider ninjas throwing Fuuma Shurikens at you. And then in Master Ninja mode you meet yet another type with swords that literally burn you when they hit you. Hard mode and above also put you against tougher versions of the cops and soldiers, specially immune to some of your techniques.
- Most of the enemies in Phantasy Star Online Episode 1 get replaced in Ultimate Difficulty by different enemies with the same basic behavior, but are usually faster, stronger, and possibly have a new elemental affinity or attacks.
- In the first episode of Redneck Rampage, Hulk Guards only appear on higher difficulty levels.
- In Terraria, Hard Mode adds new monsters from The Corruption: