In the fifth episode of "What If…?" Season 3, titled "What If…The Emergence Destroyed the Earth?", the Marvel Cinematic Universe (MCU) takes a dramatic turn into a dystopian narrative where the catastrophic event from "Eternals" unfolds without prevention, leading to the Earth's destruction. At the heart of this desolate reality stands Riri Williams, aka Ironheart, as the last beacon of hope in a world dominated by the Iron Federation led by the nefarious Quentin Beck, aka Mysterio.
The episode opens with the Watcher (Jeffrey Wright) revealing the grim fate of a universe where the Emergence of Tiamut, a Celestial, from the Earth's core occurs earlier, before the Eternals can unite to stop it. This apocalyptic event shatters the planet, leaving its remnants afloat in space. In the aftermath, Mysterio seizes control of Stark Industries, establishing the Iron Federation and using advanced technology and the Iron Legion to subjugate the surviving population.
Riri Williams, voiced by Dominique Thorne, navigates this dystopian landscape, seeking clues and resources to construct a weapon capable of toppling the Iron Federation. Her journey leads her to an old hotel where she meets Sharon Carter, the Power Broker, who betrays her to the Federation. Despite this betrayal, Riri escapes with the help of the Alliance, a resistance group comprising Admiral Ying Nan, Wong, Okoye, Valkyrie, and other survivors.
The Alliance, recognizing Riri's potential, brings her to their hidden base aboard the remnants of the Titanic, where they provide her with the tools to complete her weapon. Riri's plan is to decouple the charges on White Vision's vibranium body, causing a system shutdown and disabling the enforcer of the Iron Federation. However, as she races against time to complete her prototype, White Vision locates the Titanic, and the Alliance must defend their position.
Despite their valiant efforts, the Alliance is no match for White Vision, and one by one, they fall. Riri, in a desperate move, fuses her mind with the vibranium-infused nanotech of White Vision, becoming a human-synthezoid hybrid. Her goal is to access the neural networks that Beck uses to control the nanites forming his illusions, hoping to dismantle his control and expose the truth.
As Riri's plan backfires and she finds herself under Beck's control, the Watcher, moved by the tragedy, breaks his no-intervention rule to motivate Riri to fight back. This intervention allows Riri to defeat Beck and project the Avengers symbol across the shattered planet, inspiring a rebellion. However, this act of defiance does not sit well with the other Watchers, who view Uatu's repeated interventions as a breach of their oath.
The episode concludes with the Watcher's actions being questioned by his peers, setting the stage for potential consequences within the multiverse. Riri's victory is bittersweet, as she stands alone amidst the ruins, a symbol of defiance in a universe where hope is a scarce commodity. "What If…The Emergence Destroyed the Earth?" is a stark reminder of the fragility of existence and the indomitable spirit of heroes, even in the face of overwhelming despair.