Juggling a Cast of Characters

So I think I've mentioned that I'm juggling a cast of thousands in the Medieval France YA. I need a sense of a full royal court worth of nobles, but I also need for the reader not to get overwhelmed by all the players.

*I* also need to not get overwhelmed by all the players.

These are more than simply walk ons, but not true secondary characters. And there are a couple of traitors hidden in there, so they need to be on-screen enough that the readers don't feel cheated when their identities are reve