The trailer — screened exclusively for attendees and not released online — begins with the Guardians of the Galaxy on their ship, floating through a creepy section of space. Star-Lord (Chris Pratt) tells his crew to put on their "mean faces" because things could get dangerous. Suddenly, a body hits their spaceship. It's an unconscious Thor (Hemsworth), wearing his gladiator garb from Thor: Ragnarok (smart money is on the end of November's Ragnarok leading directly into 2018's Infinity War). They bring him inside the ship, and Mantis (Klementieff) wakes him up.

Thor looks around, sees Star-Lord and asks the natural question: "Who the hell are you guys?"

Next, we're on Earth, where our heroes are dealing with death and destruction. Loki (Tom Hiddleston) has the Tesseract (the Infinity Stone he played around with in The Avengers), and he's up to no good. In New York, Peter Parker (Holland) is on a school bus and sees his arm hair is rising (Spider-Sense?).

It's hard to break down how wild this trailer is, but here are just a few other small observations:

— Spider-Man has a new suit that looks quite advanced, a la the one at the end of Spider-Man: Homecoming or the costume from the Spider-Man 2099 comics.

— Captain America has a beard and looks like he's been through a lot. It's clear he's been off doing something away from Iron Man's Avengers and that this is their first time seeing him again.

— Thanos wears the Infinity Gauntlet and pulls down part of a moon to battle the Avengers on an alien planet.

— Doctor Strange battles alongside the Guardians of the Galaxy and Iron Man on this planet.

Brolin, whose villain, Thanos, has been teased since 2012's The Avengers, was the first star Feige brought out to introduce the trailer, and it's clear he was getting into the role.

When Feige suggested that Bautista's Drax might be able to take Thanos down, Brolin responded: "Drax ain't shit."

More and more Avengers kept stepping out onto the panel, and Feige kept asking if Brolin was nervous. The answer was always no.

Co-director Joe Russo was in Anaheim for D23, while his brother, Anthony, remained in Atlanta to continue shooting the Avengers saga. Infinity War wrapped on Friday, and they are starting work on an untitled Avengers 4.

After the panel, Marvel had one more surprise. It shared a photo of Brolin next to four statues of Thanos' team of bad guys, the Black Order. It seems Thanos won't be alone in facing the Avengers.

Infinity War opens 10 years after the Marvel Cinematic Universe launched with Iron Man. It's being billed as the capstone of a decade's worth of storytelling. It will pit most of the MCU against Thanos, a sinister alien who hopes to possess all of the universe's Infinity Stones in order to become all-powerful.

Avengers: Infinity War opens May 4, 2018.