Avengers: Infinity War and Avengers 4 will serve as a "culmination" for every story thread since 2008's Iron Man, according to co-director Joe Russo.
Russo, appearing in the Marvel Studios: The First Ten Years — The Evolution of Heroes retrospective included in the Thor: Ragnarok digital release special features, teased the two movies will act as a payoff for the first decade of the shared Marvel Cinematic Universe.
"Every story that Marvel has told since Iron Man 1 finds a narrative thread in these next two Avengers movies," Russo said. "It is a culmination of all that storytelling."
Marvel Studios president Kevin Feige says Infinity War, Marvel Studios' 19th film, will wrap up what has come before — and simultaneously chart the course for Phase 4, launching in 2019 with the unnamed Spider-Man: Homecoming sequel.
"With Infinity War, we're paying off every little thread and every little tease that we've had in what will be 18 films prior to Infinity War," Feige said.
"There's never been anything like this. Being able to, film after film, tease at a larger story. Really building these stories up into a giant conclusion. While at the same time introducing an entirely new direction for the future."
Speaking with Vanity Fair in November, Feige said the upcoming Avengers 4 will "bring things you've never seen in superhero films: a finale."
The Infinity War sequel will serve as a point of demarcation for the Marvel Cinematic Universe, Feige said, leading to "two distinct periods."
"Everything before Avengers 4 and everything after," he said, adding, "I know it will not be in ways people are expecting."
More ominously, Feige said the blockbusters will bring an end to some characters' journeys.
Guardians of the Galaxy and Guardians of the Galaxy Vol. 2 star Karen Gillan, returning as Nebula — scorned adopted daughter of Infinity War big bad Thanos (Josh Brolin) — promised the Avengers threequel is "going to be more than a movie, it's going to be a cinematic event."
"Anyone who is a Marvel fan and knows stuff from 10 years ago will see it become relevant in this," Gillan told The Hollywood Reporter in December. "It's like everything that you've known about Marvel is building to this movie."
Thor: Ragnarok is now available to own digitally and releases to 4K Ultra HD and Blu-ray March 6.
Avengers: Infinity War opens May 4, followed by Ant-Man and the Wasp July 6. Captain Marvel opens March 8, 2019, followed by Avengers 4 on May 3, 2019. Phase 4 launches with the Spider-Man: Homecoming sequel July 5, 2019.