The Mustang star Matthias Schoenaerts, Aladdin villain Marwan Kenzari and Italian actor Luca Marinelli have signed on to join Charlize Theron and KiKi Layne in the action movie The Old Guard, Collider has learned. A co-production between Netflix and Skydance Media, The Old Guard follows a small, covert group of immortal mercenaries who must fight to keep their team together when they discover the existence of a new immortal and their extraordinary abilities are exposed. Theron is starring as The Old Guard's 6000-year-old team leader Andromache of Scythia (aka Andy), while Layne will play the squad'…