Thanos, a fictional character in the Marvel Comics Universe, poses so big a threat that "Avengers: Infinity War" had to be split into two parts to accommodate his story.

Movie Pilot explained the significance of Thanos (played by Josh Brolin) in the upcoming films. The supervillain will seek out and collect the Infinity Stones and attempt to harness their power by using the Infinity Gauntlet. According to ComicBook.com, "The Infinity Gauntlet is a weapon that Thanos assembles out of the six Infinity Gems, which grants him mastery over time, space, mind, reality, power and soul."

ComicBook.com added that in the Marvel Cinematic Universe, four Infinity Stones have been introduced - The Tesseract or the Space Gem, The Aether or the Reality Gem, The Orb or the Power Gem, and Loki's scepter or the Mind Gem. These objects are known to contain great power and are highly coveted by beings who want to use that strength in their own good, Movie Pilot noted.

Movie Pilot also stated that "those who are aware of the threat of the collected stones agree that the stones should be kept separate" and that "they are scattered to hidden locations in the nine realms."

The Infinity Stones have been introduced over the course of the Marvel films. The Tesseract was featured in 2012's "Avengers." The Aether was introduced in 2013's "Thor: The Dark World" when Jane Foster accidentally found it, Movie Pilot added. It was reportedly presented in a fluid-like state and "can affect all of reality as it punches holes through time and space." The Orb, on the other hand, was featured in "Guardians of the Galaxy."

Cast and Release Date

There are rumors that the "Avengers" sequels will be directed by brothers Joe and Anthony Russo, A.V. Club wrote. The Russos are also behind "Captain America: The Winter Soldier" and its highly-anticipated sequel "Captain America: Civil War."

It's not yet confirmed whether the original superhero cast will return for "Avengers: Infinity War." MTV noted that the actors "have been pretty public about how most of their contracts with Marvel run out the same time" as the movie. There's a possibility that Robert Downey Jr. (who plays Iron Man) and Chris Evans (Captain America) will return, though.

Marvel stated in its report that "Avengers: Infinity War Part 1" will be shown in theaters on May 4, 2018, and will conclude in "Avengers: Infinity War Part 2" on May 3, 2019. On the other hand, the upcoming second film directed by Joss Whedon titled "Avengers: Age of Ultron" will premiere on May 1, 2015.