[Taqwus]

The AI, even on Normal, will definitely build labs, forts, temples, and rather large armies if you give it the time.
Sitting back and letting a single AI take 66-75% of a medium-sized map can make for an interesting slugfest, at least if you like large-scale battles with high-end magic. Mmmm, 1500+ units and 120+ commanders in a single battle, Flame Storms and Death Winds oh my!