Strangest development of other faction in your campaign?

[Os-Q]

Not really the weirdest things but interesting: In my campaign as Armenia, the Parthians swept north and drove the Saka west, who then drove the Sarmations into Olbia and the northern Black Sea coast.

In another campaign as the Sweboz, Carthage was expelled from Iberia, but destroyed my Roman allies and conquered Italy. The cities in the newly Punic Italy were underdefended however...
("Letz stomp some Karthiez!")