I'm writing a historical fiction novel, and there's going to be many scenes where people will have to address the Emperor. When the Emperor gives a command, the sentence I'm using right now in reply is: "As your imperial majesty desires." Now, I just made this up, but is this grammatically correct, and are there better alternatives? P.S. I've been reading Conn Iggulden's Conqueror series lately, and I've noticed that Iggulden uses the sentence "Your will, my lord" very often. Is this a popular sentence, or is it something Iggulden made up? Thanks!
Okay, I quess I'm not fully awake after all. I saw the title as Dressing an Emperor, and was expecting some variation on the Emperor's New Clothes metaphor.
Which emperor? There have been different rules for different places at different times. Also the degree of formality will depend on the closeness to the emperor and the formality of the court. "As your imperial majesty desires" is certainly possible, and is probably at the most formal end. It might be acceptable to say something marginally less formal, such as "as you desire, your imperial majesty" or even "as you desire" (you don't say a persons name every time you speak to them, do you?) But if it's a historical novel you need to find out what the practice was in the relevant court. For example, the Japanese emperor was "your imperial majesty" until the end of WWII but then became simply "your majesty". In China, the emperor was addressed as "emperor", and so on.
As others have suggested, this depends on the place and time. The Emperor of 19th century China will be addressed differently than the Emperor of 1st century China. The Emperor of Rome would be addressed differently than the Emperor of the Mughal Empire. And so on.