Left Hand and the Right Hand
So a Second AI, independent of the adversary AIs, could make a whole new species of better video games. Good. But it also tells us something about tabletop gaming, and that's that the GM is really wearing two hats, or to use a better metaphor, playing the game with two hands.
With the left hand, the GM controls the adversaries, the things in the game world that oppose the player characters. The left hand has to be ruthless, or more specifically, honest to the motivations of the enemies regardless of how bad it will be for the player characters. The tiger pounces and tries to eat its prey. The tiger doesn't hang back just because the nearest player character is badly wounded and could be killed.
With the right hand, the GM controls the allies, the things in the game world that are generally sympathetic to the players. Just like the adversaries, the right hand has to be honest to the allies' own motivations and knowledge. Most allies won't just fling themselves to their death to help the player characters.
Above both sits the Brain, the actual GM. The GM is on no one's side except the game itself. The goal is a good game, which does not just mean the players win. A good game may mean the players do well, other times it may mean the players have a really hard time or get wiped out. The GM might up the ante if the players are having too easy a time, because that improves the game. The GM says “hmmm, a few more ogres would make this fight more interesting,” and once they show up the left hand takes command and sends them crashing into the heroes. The left hand didn't add the ogres, the GM did.
A GM that fails to make the distinction between steering the creatures in the game world and moderating the game itself may:
a) fail to present a credible threat (having the monsters pull back when the heroes are in danger to avoid killing them)
b) play from the point-of-view of the enemy too much (grumbling when they are defeated too easily or enjoying their victories too much when they smash the heroes), or
c) have NPCs make decisions based on information they should not have (not bothering to use powers that the heroes are immune to)
In computer terms, the GM's left hand and right hand are traditional AIs, controlling creatures in the world, but the GM also serves as the Second AI, watching over the game as a whole.
The trick is to keep the roles separate. Will it really help your game to imagine that you are using different hands to control different creatures? Try it and see.