What to wear: For I-Just-Blew-Everyone-Up Cersei, wear short blond hair, a crown, a long black long-sleeved dress, and some kind of silver designs for your shoulders. If you want to go the extra mile, stick a bunch of fake swords to your back so it looks like you're sitting on the Iron Throne no matter where you are.
How to act: Cersei always has the best, most cutting comebacks, so make sure you're on your game on Oct. 31. Also, have a glass of red wine to swirl around threateningly at any given moment.