Good grid.
Couple of minor points:
Caspian is misspelled.
The Tsar group should, but does not, accept "rulers" as a connection.

Thanks Nighteyes, apologies about the spelling though, it's not my strong point even when I double check them 🙈

The points Nighteyes made are the only things letting this grid down

Only took a few secs as I predicted the Macaroni red herring but I did used to work with penguins! Difficulty relies on that one herring, I think, but it's a great starting point for a grid.
As to poor spelling- if you struggle with your name, should you be running a country??????? ;)

Good grid, minor issue that king and emperor are completely interchangeable in their groups, so there more than one solution.

Great grid, loved it.