User:MarioProtIV/616

In the Marvel Cinematic Universe, Earth-616 or the Sacred Timeline, is the main continuity for most media depicted within the MCU and its associated media.

Designation
Earth-616 is the main designation for the main MCU universe. Despite having been designated as "Earth-199999" by Marvel Comics in 2008, Multiverse of Madness establishes the MCU as Earth-616, sharing the name with the primary setting of the comics. Marvel Studios executive Nate Moore previously referred to the main MCU universe as Earth-616 in November 2021, and Feige also began using the term internally prior to the release of Multiverse of Madness. In addition to Beck's ruse of the term in Far From Home, a reference to the "616 universe" can be seen on Erik Selvig's chalkboard in The Dark World.

History
The beginning of Earth-616 started with the Big Bang, sending the six Infinity Stones hurtling across the universe.

Branched timelines
Several MCU projects have explored possible deviations in the main Sacred Timeline, beginning with Avengers: Endgame (2019), What If...? (2021–present) and Loki (2021–2023). Some of these branches of resulted in vastly different events unfolding depending on the scenario, such as a zombie apocalypse occurring, the destruction of Earth or the Time Heists during the events of Endgame.

Destruction of Earth
After learning of Thanos' army's assault on Earth in search of the Mind Stone, and a prophecy heralding the destruction of Earth on the same day in the fifth season of Agents of S.H.I.E.L.D. (during the events of Infinity War), a gravitonium-infused Glenn Talbot, intending to assist the Avengers in their battle against Thanos' army,   attempts to draw more gravitonium from the core of the Earth to increase his power, inadvertently destroying the Earth and fulfilling the prophecy he intended to avert. In the main events of the season, Phil Coulson and his agents are transported to this future from 2017, learning that their future selves, on failing to prevent the destruction of Earth, instead saved a small portion of humanity inside S.H.I.E.L.D.'s Lighthouse base, now in orbit around Earth's remains as a makeshift space station. After returning to their own time, in 2018, six months after they left their original universe, Daisy Johnson blasts Talbot into space before he can accidentally destroy the planet.

2012 Time Heist
The Avengers visit New York City in an alternate 2012 during the Battle of New York in Endgame. While Bruce Banner / Smart Hulk implores the Ancient One to relinquish the Time Stone, Rogers intercepts a S.T.R.I.K.E. team and acquires Loki's scepter containing the Mind Stone. Stark and Lang attempt to thieve the Tesseract from Stark's alternate counterpart, but the plan goes awry and Loki escapes with the Tesseract. In Loki, this reality is "reset" by the TVA and the alternate Loki is arrested.

2014 Time Heist
During the Avengers' Time Heist in Endgame, Natasha Romanoff / Black Widow, Clint Barton / Hawkeye, James Rhodes / War Machine, and Nebula time-travel to an alternate Morag in 2014. Romanoff and Barton depart on the Benatar to Vormir to acquire the Soul Stone, in which Romanoff sacrifices herself. Meanwhile, Rhodes and Nebula successfully acquire the Orb containing the Power Stone, but Nebula is captured by the 2014 Thanos. Later, 2014 Thanos and his warship, the Sanctuary II, are teleported to the Avengers Compound in 2023, leading to a major battle between Thanos' forces and the Avengers, Guardians of the Galaxy, Masters of the Mystic Arts, Wakandans, Asgardians, and Ravagers. An alternate version of Gamora from 2014 betrays Thanos and joins 2023 Nebula, later disappearing from the battlefield. She returned in the film Guardians of the Galaxy Vol. 3 (2023).

Zombie apocalypse
In a reality first explored in "What If... Zombies?!", Pym rescues Janet from the Quantum Realm as he did in the film Ant-Man and the Wasp (2018), only to discover that Janet has been infected with a quantum virus which transformed her into a zombie. This leads to a zombie apocalypse, with many Avengers turned into zombies, including Stark, Strange, Wong, Barton, Happy Hogan, Sam Wilson / Falcon, Sharon Carter / Agent 13, Rogers, and Maximoff. This reality will be revisited in Marvel Zombies, in which additional characters are revealed to have transformed into zombies, including Emil Blonsky / Abomination, Ava Starr / Ghost, Carol Danvers / Captain Marvel, Okoye, and Ikaris.

Ultron's conquest
The episode "What If... Ultron Won?" of the first season of What If...? is centered on an alternate reality where Ultron transfers his consciousness into the Vision's body, acquires the Infinity Stones from Thanos, and wipes out all life in the universe. This leads into the first-season finale, "What If... the Watcher Broke His Oath?", in which the Watcher assembles six multiversal characters from the previous episodes to the Guardians of the Multiverse, and Ultron is defeated. The animators used an artistic effect called the Kirby Krackle in these two episodes to demonstrate the multiversal power of Ultron and the Watcher, which Bradley was adamant on including due to it never having been used before in the MCU.