Lots of movies have dozens of characters in them. In this one, many of them just happen to be wearing costumes because that's the world it's set in. Doesn't mean they all have to have plots and story arcs--some will just be short appearances or background. You should look up how many named characters there are in Titanic (they're all wearing period costumes instead of superhero costumes) or some of the Harry Potters. And the LotR movies... don't watch those whatever you do if you don't like movies with a lot of characters! I think there's, like, over a hundred. The Godfather has a crapload, too, I seem to recall.
I guess you'll have to wait and find out..