Be warned, this story contains massive spoilers for X-Men: Days of Future Past, so read on at your own risk.
Following yesterday's /x-men-apocalypse-is-coming-may-2016-bryan-singer-will-direct/huge news that X-Men: Apocalypse is set for a 2016 release, many fans have wondered how this villainous character will be introduced into the franchise. Today, we have a report that reveals the mid-credits sequence for X-Men: Days of Future Past, which offers a few huge surprises.
This information comes from one of the most recent drafts of the X-Men: Days of Future Past script. While there is reportedly a set piece that was changed in the final version of the film, that change doesn't effect this scene below.
The scene shows Michael Fassbender's Erik Lehnsherr in a run-down house in the middle of nowhere, when the massive alien Apocalypse appears, described as, "towering, terrifying, with a twisted metal face and dark pits for eyes." Apocalypse says, "I have crossed rivers of time to find you," to which Magneto replies, "Who are you?" Apocalypse says, "I am your future," before suddenly merging with Magneto, causing an energy explosion that destroys everything within a few miles of the blast. Magneto begins to realize what kind of power he now wields, and flashes an evil grin before the film cuts to black.
With all that being said, X-Men: Apocalypse will likely follow only the cast members from X-Men: First Class, and not other characters from X-Men: Days of Future Past, although the future timeline could still come into play. It isn't known if X-Men: Apocalypse will jump back and forth in time or not, but this Magneto/Apocalypse connection could result in two separate timelines, one with the younger Magneto (Michael Fassbender) possessed by Apocalypse, and the future timeline with the older Magneto (Ian McKellen). However, it isn't known if Apocalypse will stay inside Magneto the whole time, as they could separate at some point and become individual villains. That's all speculation at this point, though, since this turn of events doesn't coincide with any of the comic book story lines.