If you saw "Marvel's The Avengers" this weekend and stayed to watch the credits, you got to see an extra scene after the main titles ended. Marvel Studios has a tradition of planting bonus scenes at the very end of their movie as a treat for fans, starting with Samuel L. Jackson's first appearance as Nick Fury at the end of "Iron Man."

But the scenes at the end of the previous movies have all been about setting up "The Avengers." Now that the team-up finally happened, fans wondered what they would tease at the end of it. The answer, obviously, was "The Avengers 2."

The mid-credits scene seems to have revealed who the villain of the next installment would be. And for diehard fans of the comic books, the revelation was both shocking and highly satisfying (if the person sitting next to you at the theater audibly gasped, they obviously were true fans). But if you aren't versed in Marvel lore, you might have been left scratching your head.

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If you want to know more about who the mysterious figure is, keep reading. Naturally, this is a big SPOILER, so if you haven't seen the movie yet, don't scroll down past this video.

Last chance: stop reading if you don't want to be spoiled.

The scene shows The Other, the leader of the Chitauri -- the alien race recruited by Loki in his attempt to vanquish the Earth -- talking to the mysterious figure sitting on a throne he has been reporting to throughout the film. The Other says that they were mislead by Loki and that humans are stronger than they believed. He tells the figure, "To challenge them is to court death." The figure turns, revealing the purple face and glowing eyes of Thanos.

"Who?" you might be asking. Thanos, the Mad Titan, is a villain who has been part of Marvel Comics since his first appearance in "Iron Man" #55 in 1973. He is an Eternal, a species originating on Saturn's moon, Titan. And he is bad news.

Thanos loves and worships Mistress Death, a physical embodiment of death that appears in Marvel Comics. Badass Digest explains that's why Thanos smiles when The Other uses the phrase "court death": "Because Thanos would like to LITERALLY COURT DEATH, as in take her out for a drink and a movie and back to his place to look at his etchings (in his face)."

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Needless to say, Thanos does not get along well with The Avengers. In the comics, he obtained the Cosmic Cube (the blue box of energy that Loki stole in the movie), and it gave him godlike powers. The Avengers teamed up with Spider-Man and The Thing in order to stop him. Later he gained control of the Infinity Gauntlet, a glove studded with gemstones that gave him control over time, space, and reality. To impress Mistress Death, Thanos kills all of the superheroes on Earth (though, of course, they eventually come back).

In an interview with /Film, writer/director Joss Whedon discussed why he wanted to include the character in "The Avengers." Whedon said, "He for me is the most powerful and fascinating Marvel villain." He went on to joke, "He's the great grand daddy of the badasses and he's in love with death and I just think that's so cute." He explained that he wanted to have someone behind Loki's machinations in the film, and that Thanos was the character in the Marvel Universe that fit the bill.

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Whedon would not confirm that this means Thanos will be the main adversary in "The Avengers 2," but it stands to reason it will take some unearthly force to bring Earth's mightiest heroes back together again. Or maybe it just takes good food. There is one additional bit of footage at the very end of the credit roll. Inspired by Tony Stark's declaration after defeating the alien invasion, there is a quick look at Iron Man, Thor, Captain America, Black Widow, Hawkeye, and Bruce Banner sitting at a restaurant eating shawarma. This looks to be the last-minute shoot that Robert Downey Jr. revealed during a press conference for the film just a few weeks ago.

There's no word yet on when we can expect "The Avengers 2," but "Iron Man 3" is slated for release less than a year from now on May 3, 2013. "Thor 2" will follow on November 15, 2013, and "Captain America 2" is scheduled for April 4, 2014.

[Photos: 'The Avengers' Five Film Facts]

Watch more clips from 'Marvel's The Avengers':

Clip: Interrogation Clip: Face Off Clip: Desperate Clip: Another Bout