Actor Joseph Quinn has been added to the cast of the 'Gladiator' sequel. The 'Stranger Things' actor will play Roman Emperor Caracalla in the Sir Ridley Scott-directed follow-up to the 2001 movie. While it has been confirmed that Paul Mescal will take on the role of Lucius - the son of Connie Nielsen's character Lucilla and Joaquin Phoenix’s Commodus from the original film, specific details about the flick remain a closely-guarded secret.