Fourteen years after Emergence Day. Marcus Fenix, a former COG soldier, is reinstated into the military after spending four years in prison for abandoning his military post in order to make a vain attempt to save his father, Adam Fenix.

The COG continues its fight against the Locust horde, who are attempting to sink all of the cities on the planet Sera by using a big riftworm to eat the ground beneath them. Sergeant Marcus Fenix leads Delta Squad into the depths of the planet to try to stop the worm from eating but instead they discover the true intent of the Locust actions.

Eighteen months after the fall of Jacinto, the Gears have moved to the island of Vectes and are living aboard a converted aircraft carrier called the Raven’s Nest. The COG has disbanded and the imulsion that powered Sera’s cities has infected and mutated members of the Locust, causing them to become Lambent. The Lambent are evolving into a new enemy that threatens both the Locust and humanity.

Kilo Squad is put on trial for various crimes by Colonel Ezra Loomis and is given the chance to explain their actions.

Similarly to the previous entries of the series, the game is primarily an online multiplayer title offering several game modes, including large-scale Warfare, Capture-the-Flag, and Death match. It also includes an extensive offline single-player game with an in-depth story, beginning with a simple tournament ladder and including team members with unique personalities.