Here's a screenshot of the issue:

I just attacked (and conquered) the city.
Now there are MANY weird things here, as shown in the screenshot:
1) Enemy units are still in the city, here asiariliih (what a name...) and a pioneer. She should be dead. I mean, I attacked her and took the city, what's she doing there with her fellow pioneer?
2) Why can I give her orders? I mean, it's weird to say the least. She has my icon instead of Magnar's but... Where does she come from?
3) The fact she's written with 'sovereign' makes me believe she is/was the sovereign of some place. But no, my enemy is Magnar, not her. She might have been Magnar's wife? What is this dude? Where does she come from?
4) All those nice buildings. I can't build them but they remain and still have an effect. I see a BIG problem here. What happens to empire buildings when you take them over? They stay. This means, in MP, it will probably be a good idea to "trade" cities with neighbours if you can just in order to get special buildings. This may also be true between Kingdoms with different strengths, but really, it's unsettling. Those buildings shouldn't be USABLE by Kingdoms. I should have to raze them and replace them with something useful, or they should turn into something Kingdoms build naturally.