UPDATE: Antonius has been confirmed to be President Snow's minister, a newly created character for the films. (Thanks to TheWrap and our friends at PanemPropaganda for the confirmation!)
A new character has been cast for Mockingjay! It seems splitting the movie into 2 parts has allowed the production team to expand on the story a little..
Welcome Robert Knepper as 'Antonius' - we can't wait to see you on screen!
Robert Knepper cast as Antonius in @TheHungerGames: Mockingjay Parts 1&2
— Lionsgate News (@LionsgateNews) December 11, 2013