For a big chunk of the 12 (for now) movies of the Marvel Cinematic Universe, the big driving force of the action has been the villainous Thanos’ search for the Infinity Stones, six big MacGuffins that will presumably give him some kind of ultimate power just in time for the Avengers: Infinity War two-parter in a few years.
The big problem is that, although the Infinity Stones have a deep history in the comics the movies draw inspiration from, they haven’t actually been explained very well in any of the movies (though Guardians of the Galaxy and the second Avengers got close). A new featurette from the upcoming Age of Ultron Blu-ray seeks to explain what’s going on with the Stones, and the various ways (most of) them have popped up in MCU going as far back as Captain America: The First Avenger. Check it out:
In a nutshell, so far we’ve seen: the space stone (aka the Tesseract from Captain America and The Avengers); the reality stone (aka the Aether from Thor: The Dark World); the power stone (the orb from Guardians of the Galaxy) and the mind stone (Loki’s scepter in both Avengers movies, currently nestled in the Vision’s forehead).
Per the comics, there are two stones – the soul stone and the mind stone – yet to be revealed, which will presumably be explored in Marvel’s upcoming slate of movies, collectively dubbed “Phase Three.” That kicks off with Captain America: Civil War, which hits theaters in May. Avengers: Age of Ultron releases on Blu-ray and DVD on Oct. 2, and is currently available on most video-on-demand services.