Csar... the word "kaiser" means "emperor" in German

And speaking of which, IC:

To the King of the Britons Ethelred the Unready

Spoiler Alert, click show to read: 
After careful consideration, His Most Pious Majesty Holy Roman Kaiser Otto the Third has decided that he wishes to conduct negotiations with your Eminence. He would be most appreciative if you were to send a representative to the Imperial Court at Frankfurt in order to engage in discussions of a diplomatic nature. It would please der Kaiser further if you would audit your military assets so as to streamline possible military-cooperation discussions.


Regards,
Baron Sigmund von Wilhelm of Bavaria
Deputy Commissioner of Kaiser Otto the Third of the Holy Roman Empire