I've previously featured Mark Strong's 'Matai Shang' costume from John Carter, which was on display at ArcLight Sherman Oaks cinema, but this version at the El Capitan Theatre in Hollywood on March 15, 2012, also sported the meddling Thern's medallion to complete the look.
Costume worn by Mark Strong as Matai Shang in John Carter
Thern medallion from John Carter
In Disney's John Carter, the mysterious Therns travel from planet to planet in our solar system using these medallions, masquerading as the native population they manipulate events to shape the future to their liking.
John Carter movie exhibit at the El Capitan Theatre in Hollywood
Go further behind-the-scenes with this book: The Art of John Carter: A Visual Journey