EDITOR'S NOTE: This article is part of a series, "Countdown to Endgame," which looks back at the films of the Marvel Cinematic Universe leading up to Avengers: Endgame.

With a second Avengers film earning more than $1 billion worldwide, and two new properties in the Guardians of the Galaxy and Ant-Man exceeding commercial and critical expectations, the Marvel Cinematic Universe showed no signs of losing momentum as it entered the third phase of its Infinity Saga. With the MCU now actively building toward the announced Avengers: Infinity War and its then-untitled sequel, the shared cinematic universe began to consciously pick apart its two ensemble properties while introducing its most unabashedly supernatural character yet in Doctor Strange.

Phase Three began with the biggest risks the studio had taken since The Avengers four years earlier, as filmmakers pitted fan-favorite heroes against each other, and the movies got weirder and more personal. Phase Two began with the MCU deconstructing its three core solo properties; Phase Three would try its hand at deconstructing audiences' expectations for the shared universe.

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Phase Three kicked off in 2016 with Captain America: Civil War, with development beginning on the sequel months before the release of Captain America: The Winter Soldier. Impressed by test screenings of The Winter Soldier, Marvel re-signed Joe and Anthony Russo in February 2014 to direct the follow-up; returning screenwriters Stephen Markus and Chris McFeely began work months before that. Exploring the fallout of the previous film and Avengers: Age of Ultron, the story appropriately focused on Steve Rogers and Tony Stark, both of whom were haunted in their own ways from the two preceding films, while Bucky Barnes' murderous legacy as the Winter Soldier provided the ultimate breaking point for Earth's Mightiest Heroes.

Chris-Evans-and-Robert-Downey-Jr-in-Captain-America-Civil-War

Deep in development, Marvel Studios struck a deal with Sony Pictures that not only led to the co-production of a rebooted Spider-Man franchise, but also brought Peter Parker into the MCU. As a contingency in case the agreement couldn't be reached in time, the filmmakers increased the role of Black Panther in Civil War, and afterward decided to maintain T'Challa's prominence the final film, even after Spider-Man was secured. Critically acclaimed, Civil War became the fourth MCU film to earn more than $1 billion worldwide. The film's impact reverberate across the MCU for years, dividing Earth's heroes when they needed to be at their most unified as the Infinity Saga reached its climax.

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Even as the Avengers fractured, Marvel embraced the supernatural possibilities of its cinematic universe, after previously waving away previous hints in the first two Thor films with sci-fi explanations. With Phase Two entering its final stages, the studio signed Scott Derrickson, then known primarily as a horror filmmaker, to direct Doctor Strange. He developed the story with screenwriter Jon Spaihts and Marvel Studios President Kevin Feige, with Spaihts convincing the other two that the film should be an origin story rather than introducing the Sorcerer Supreme already settled into his role. Feige switched the planned original antagonist Nightmare with Dormammu, given the villain's prominence in the comics. With Benedict Cumberbatch, the original choice to star, initially committed with other projects, the filmmakers began searching for other candidates before deciding to delay the film's release by three months to accommodate Cumberbatch's schedule.

Dr. Strange using the Time Stone in the MCU

With a supporting cast that included Tilda Swinton, Chiwetel Ejiofor, Rachel McAdams and Mads Mikkelsen, production took place in London and on location in New York, Hong Kong and Nepal. Unapologetic in its depiction of the paranormal, Derrickson blended psychedelia, surrealism and classical art to create the film's visual look, and officially bring magic into the heart of the MCU. Audiences and critics alike responded well to the genre deviation, making Doctor Strange the highest-earning debut solo MCU film at the time while boasting an impressive 89 percent critics' score on Rotten Tomatoes.

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The first two films of Phase Three took place firmly on Earth, but its third installment returned to the cosmos in Guardians of the Galaxy, Vol. 2. Within a month of the original film's release, James Gunn was already hard at work writing a sequel, with his progress moving up Vol. 2's release date by more than two months. The core cast of the previous film returned, with the notable additions of Kurt Russell as Ego the Living Planet and Pom Klementieff as his assistant Mantis. Early drafts also introduced Adam Warlock, although Gunn removed him so as not to overcrowd the story, but retained a hint to the character's future in a mid-credits scene.

Guardians of the Galaxy Vol 2 Ego

While not really a risk in comparison to the first two Phase Three films, Vol. 2 is one of the most personal, and emotionally raw, installments of the MCU. Star-Lord is confronted by a father who harbors his own sinister secrets; Gamora and Nebula navigate their complicated relationship as siblings; and the reasons for Rocket Raccoon and Yondu's standoffish natures are fully explored. If the original Guardians of the Galaxy was about an unlikely family coming together, its sequel was about a family getting to know each other and deciding whether it should ultimately stay together. Instead of going bigger for the sequel's story, Gunn went deeper. With a new retro soundtrack and leaning more into vibrant imagery, the film was an even bigger commercial success than its predecessor, although audiences were a little more divided about how the sequel compared to the original.

In its initial three installments, the MCU went darker, stranger and more emotionally vulnerable than ever had before. The final act of the Infinity Saga came out the gate with its most visible team split right down the middle, while the subsequent two films introduced magic to the cinematic universe and doubled down on its cosmic aspirations. Conscious of this, the following three films would look to re-instill a sense of escapist fun that had built the MCU in the first place, while expanding the roles of two newly introduced superheroes.

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