I talk about enemy progression and basic techniques to put together more difficult enemy encounters.
Since
StrongBelwas doesn't seem to be up to doing the summaries anymore, I may as well try my hand at one considering that this is a topic I'm actually fairly interested in.
Cain starts out by addressing a comment asking him to talk about "enemy scaling". He then differentiates enemy scaling and enemy progression:
-Enemy scaling is essentially level scaling. Your numbers get bigger and your gear gets better, enemies follow suit. He isn't a fan of this type as he feels that it's illogical for e.g. a bandit to still be a bandit when they could retire off of selling their equipment.
-Enemy progression is a creature or group of creatures naturally getting harder as the player grows in strength without artificially increasing numbers.
Enemy progression consists of two main factors: the number of enemies and variety in enemies. Variety can mean variety in individuals - individual creatures do more things - and variety in groups - where there are different types of creatures.
Cain uses an example with bandits to showcase enemy progression. The first encounter with a bandit is just one single bandit, the second is against a couple of bandits with different tactics and equipment, the third is against a few more bandits with different equipment or support in the form of attack dogs. He uses this example to illustrate a "bandit encounter" getting harder and harder by increasing the number of enemies and what capabilities those enemies have.
Increasing the number of enemies is easy, so Cain talks more about variety, specifically attack variation. You can give enemies different types of attacks - melee units, ranged units, etc. Ranged units with area of effect attacks seem to be a personal favorite as they can hit multiple targets as well as around cover. Another way of increasing attack variation is simply by giving the enemies better gear, but within reason - no bandits wearing Glass armor.
Another way of forcing attack variety is by giving enemies limited use weapons, for example a rocket launcher with only one rocket, or a gun that takes a long time to reload that forces the enemies to switch to a faster weapon thus requiring the player switch up their tactics mid-fight. Attack variation can also be introduced by different movement speeds - enemies that sprint, jump, hover above the player and use ranged fire(with the caveat that there needs to be a way for melee-only characters to bring them down).
Various other methods are adding enemies mid-fight through for example a summoning spell, environmental elements such as traps or cover, and adding attacks that change the environment such as setting things on fire through fire-breathing or acid spitting.
So, to summarize - enemy progression is defined by the number of enemies you throw at the player, and how varied those enemies are - both in how they attack, move, or change the battlefield around them, and which types they are - mixed melee and range, enemies from two different factions attacking you at once, or enemies requiring certain items. For the last one, he uses an example of a wizard who can summon undead that the player needs holy water or cleric spells to put down.
Cain concludes by saying that he thinks this is a better way of doing combat progression rather than just pumping up stats and giving all the enemies ridiculously good gear.
TL;DR: Enemy progression is more engaging when done with numerous enemies with varied roles and abilites than when done by just increasing numbers.