IMO the broken loyalties spell from Kraxis racial betrayal need some change. I found it is ridicules AI was able to take over fully stationed city (include sovereign and champion.) that has low unrest. My game even bug out at that point due to some of stationed unit retake the city right away and prevent me to do anything later.
I checked the xml file and found broken loyalties spell doesn't cost mana and only cost 1000 gold (which is nothing at later of game.) I thihnk borken loyalties spell should only be able to cast on city that has really high unrest. I mean why would a city change side for 1000 gold when they are happy?