The Marvel Cinematic Universe has officially welcomed the X-Men. A new teaser for Avengers: Doomsday places Patrick Stewart's Professor Charles Xavier, Ian McKellen's Magneto and James Marsden's Cyclops front and centre, marking the first time these iconic characters from the 20th Century Fox era appear together under the MCU banner. The teaser, which surfaced online after a week of leaks before its official release, opens at Xavier's School for Gifted Youngsters. Once a symbol of hope and safety for young mutants, the school is now shown in ruins.