You better look worried, Cap. Things are about to get rough for the Avengers. Marvel Warning: If you haven't seen "Avengers: Age of Ultron" there are major spoilers ahead!

If you're heading out to see the "Avengers" sequel this weekend, don't head out right after the movie is over.

Although there won't be any added scenes after the entire credits roll, there is one brief mid-credits sequence that appears right after the initial credits.

If you left early or are confused by what you saw, here's what you should know.

What happens:

The scene opens over an object shrouded in darkness. When it comes into view, we see it's a golden glove — the Infinity Gauntlet.

We then get another glimpse of Thanos (Josh Brolin), the somewhat mysterious, big bad villain who we've been seeing teases of since the end of 2012's "The Avengers." He reaches out toward the audience to grab the gauntlet. As he puts it on he says, "Fine, I'll do it myself."

Just imagine Josh Brolin with light purple makeup and a nicer gauntlet without all those colored gemstones. Joe Scarnici/Getty Images for Disney That's it! (We told you it was short.)

In order to explain what this means, let's break this down into a few items.

What you need to know about Thanos

Thanos has a giant grudge against the universe for being born different. He's essentially the Hunchback of Notre Dame of the Marvel Universe, but with a spine.

Thanos was born into a group of superhumans, the Eternals, who live on Saturn's moon, Titan. However, when he was born, he didn't look like any of the other Eternals.

In comparison, here's how his brother, superhero Starfox, looks:

As you can see, the two look nothing alike. You can kind of see why Thanos may be angry with the Gods. Marvel Also known as the Mad Titan, Thanos became power hungry and obsessed with death. (Not only is he obsessed with killing others, but in the comics he is actually in love with the embodiment of Death itself. More on this in a bit.)

In the Marvel Cinematic Universe, he's obsessed with gathering and gaining control of the Infinity gemstones and the Infinity Gauntlet to unleash their power. It's noted in "Guardians of the Galaxy" that Thanos is responsible for the death of Drax the Destroyer's (Dave Bautista) family. He's also the ruler of the Chitauri, the alien race that invaded Earth in the first "Avengers" film.

What kind of powers does this guy have?

Josh Brolin takes the stage at San Diego Comic-Con with the "Avengers: Age of Ultron" cast to show off the Infinity Gauntlet. Alberto E. Rodriguez/Getty Images You name it, and Thanos essentially has it.

Since Thanos comes from the Eternals, he has every ability endowed to them including super strength, endurance, and agility. Marvel describes his skin as being virtually impenetrable. It can withstand "heat, cold, electricity, radiation, toxins, aging, and disease." A psychic attack most likely won't affect him either. (Sorry, Scarlet Witch.)

Thanos can also blast "cosmic energy" from his eyes and hands.



If all of that isn't enough, Thanos was also granted immortality by Death itself.

So, yeah, The Avengers sound screwed.

So, what is this Infinity Gauntlet item Thanos is after?

The Infinity Gauntlet can be spotted briefly in 2011's "Thor." Marvel This is what the Marvel Cinematic Universe has been building toward for some time!

Through all of the Marvel movies, there has been an entirely larger story arc told in the background, often through the end-credits scenes, where Thanos has attempted to secure several powerful stones for the Infinity Gauntlet, which he had crafted. When it's combined with six Infinity gemstones, the person in possession receives, in so many words, infinite power.



And, what are the Infinity stones?

We've already been introduced to most of these throughout the Marvel movies. The stones on film appear to differ slightly from the ones introduced in the comics, which have varied over time.

Benicio del Toro's character, The Collector, describes the origin of the stones in 2014's "Guardians of the Galaxy":

"Before creation itself, there were six singularities. Then the universe exploded into existence, and the remnants of these systems were forged into concentrated ingots. Infinity Stones. These stones, it seems, can only be brandished by beings of extraordinary strength."

The Collector then showed footage of what looked like mercenaries who have used the stones before to destroy entire civilizations.

As Thor (Chris Hemsworth) notes at the end of "Age of Ultron," so far, we've only seen four of the six gemstones on screen.

Blue (introduced in "Thor"): The space stone, also known as the Tesseract, is currently at Thor's home in Asgard being watched over by Heimdall (Idris Elba).

Marvel Red (introduced in "Thor: The Dark World"): The Aether was desired by Malekith in order to make the universe black. The Collector is still believed to have it. It's not clear whether it was lost in the shuffle that happened in "Guardians of the Galaxy."

Jane Foster (Natalie Portman) discovers the Aether in "Thor: The Dark World." Disney / Marvel screencap Yellow (introduced in "Avengers: Age of Ultron"): The mind stone was held in Loki's Chitauri scepter and is now in the Vision's head. (That's not a good sign for him moving forward.)

We're really nervous about how Thanos is going to get that yellow gemstone. Marvel Purple (introduced in "Guardians of the Galaxy"): The power stone is currently being held onto by the Nova Corps on Xandar. The Guardians were able to wield its power together.

Peter Quill (Chris Pratt) stumbles upon an orb holding the purple power stone in "Guardians of the Galaxy." Disney/Marvel



Why does Thanos want the Infinity Gauntlet?

Basically, Thanos wants to wipe the existence of most life from the universe. In the comics, this is done to impress and win the adoring affection of the aforementioned physical form of Death.

Yes, you read that right.

Not only is the Mad Titan obsessed with the idea of death, but he is also head over heels in love with Death.

It's not clear whether this is something the Marvel films plan to touch upon moving forward.

What the end-credit scene means:

If you've been following all of the mid-credits and end-credits scenes from Marvel films closely, Thanos has been trying to acquire all of the Infinity gemstones. Having failed a number of times to acquire them (first in "The Avengers" after making a deal with Loki to acquire the Tesseract, and later in "Guardians of the Galaxy"), Thanos is finally taking matters into his own hands.

So while many of the Avengers are taking a break from superhero life at the end of "Age of Ultron," and Thor is off trying to figure out why the gemstones have been popping up, little do they know that things are just starting to get interesting.