The third teaser trailer for “Avengers: Doomsday” officially confirmed the long-rumored return of iconic X-Men characters: Cyclops (James Marsden), Professor Xavier (Patrick Stewart) and Magneto (Ian McKellen) to the Marvel Cinematic Universe (MCU). The trailer, which debuted on Tuesday, Jan. 6, opened with gloomy dialogue about death between Stewart’s Professor X and McKellen’s Magneto.  “Death comes for us all,” pondered Magneto. “The question isn’t whether you are prepared to die. The question is: Who will you be when you close your eyes?” Marsden’s Cyclops then appears in action, tearing off his visor to unleash a powerful optic blast amid ruins. […]... Keep on reading: X-Men characters Cyclops, Professor Xavier, Magneto return to MCU