Improves AI diplomatic, war, and city development strategies.
Eliminates the AI growth and happiness bonuses.
Shifts AI science/production bonuses from early to late game. This alleviates the classic problem in Civilization games where early eras are much harder and important than later eras.
Provides militaristic bonuses for AIs on higher difficulty levels. (Vanilla has only economic bonuses, giving combat a disproportionate influence on high difficulties.)
Added a science bonus for AIs based on difficulty level, and reduced other AI bonuses. Details
AI starting units focus more on archers/triremes/workers than vanilla (which gives warriors/workers).
When an AI capital is near lots of water, the AI starts with triremes and embarkation.
Citystates start with defensive units.
Citystates can upgrade units for free.
Ancient ruins near AI capitals auto-acquire. Each ruin gives a small amount of gold, science, and culture similar to averaging all the possibilities. The randomness of early AI exploration is a major problem in vanilla.
Barbarians cannot enter civilized territory until a turn which depends on difficulty level.