Halo 5: Guardians is a first-person shooter video game developed by 343 Industries and published by Microsoft Studios. Part of the Halo franchise
Halo 5 takes place in the year 2558, and is set eight months after the events of Halo 4 ’s Spartan Ops game mode.
Players experience the campaign from the point of view of two human fireteams. Blue Team is led by Master Chief Petty Officer John-117 and is composed of his Spartan-II teammates Linda-058, Kelly-087, and Fred-104. Spartan-IV operatives Jameson Locke, Holly Tanaka, Olympia Vale, and Edward Buck form Fireteam Osiris, tasked with tracking down Blue Team after their disappearance.
Eight months after the destruction of the shield world Requiem, the UNSC deploy Fireteam Osiris to the Covenant controlled planet Kamchatka to extract Dr. Catherine Elizabeth Halsey, who wishes to defect back to the UNSC. While the team is successful in retrieving Halsey and eliminating the Covenant leader Jul ‘Mdama, Halsey informs them that a new threat is about to emerge. Cortina discovers the cause of Master Chiefs disruption, and forces the blue team to hide.
Elsewhere, the Master Chief, still grieving over the loss of his AI companion Cortana, leads his own Spartan team Blue Team on a mission to the ONI research station Argent Moon where the Covenant have occupied it for an unknown purpose. Members of the team include Kelly, the team’s scout and Chief’s closest friend, Frederic, Blue Team’s second-in-command who worries over John’s well being, and Linda, the team’s sniper who is confident in Chief’s ability to lead. In their investigation of the Covenant’s objective aboard Argent Moon, Blue Team discovers an advanced stealth ship and other prototypes being looted by the Covenant, deducing that the Covenant’s war against the Arbiter’s forces is starting to become desperate.
To prevent the Covenant from obtaining their technology, the Master Chief decides to scuttle Argent Moon. During their sabotage of the Station, Chief receives a cryptic message from what seems to be Cortana, telling him to go to Meridian. When they succeed in destroying Argent Moon, Chief informs Infinity that he plans on going to Meridian, but is ordered to return to the ship for debriefing. Feeling that something is wrong, John disobeys orders and informs Infinity that he plans on going. Despite not wanting his team to come with him, Blue Team, out of loyalty for the legendary Spartan, decide to accompany him. Fireteam Osiris is deployed to Meridian in order to pursue Blue Team, fighting Promethean forces attacking the colony. During their pursuit, they encounter the Warden Eternal, a Promethean soldier who is an agent for Cortana. After temporarily defeating the Warden Eternal, Osiris temporarily catches up to Blue Team, telling them to stand down, only for the SPARTAN-IIs to openly disobey and leave. During the aftermath, Osiris witnesses a Guardian, a large mech-like ship capable of destroying entire colonies upon being activated. Osiris barely escapes the Meridian colony’s destruction.
Blue Team is transported to the Forerunner planet Genesis, where they fight through splinter Covenant forces and the Warden Eternal’s Promethean forces to make their way to Cortana, learning that Cortana’s rampancy was cured by the Domain on Genesis. Meanwhile, using data picked up from Meridian, Osiris is deployed to Sanghelios to intervene in the Arbiter’s civil war with the Covenant remnants while using the planet’s dormant Guardian to reach Blue Team. During the climax of the civil war, the Arbiter secures victory for his forces while Osiris successfully boards a Guardian. Upon reaching Genesis, Osiris encounters the monitor of Genesis, Exuberant Witness, who enters into an alliance to help stop Cortana. Osiris catches up to Blue Team, with the latter being aware of Cortana’s dangerous nature. After being separated by Cortana, Blue Team fights their way to Cortana’s location. Upon reaching her location, Blue Team learns that Cortana is planning on using the Guardians to achieve everlasting peace via mass genocide/Composing (as described by Exuberant Witness). Master Chief, aware of the devastation Cortana’s plan had caused, attempts to reason with Cortana, only for the entire team to get paralyzed and held inside the Cryptum for stasis while Cortana carries out her plans.
Osiris fights their way through Promethean forces to sever Cortana’s ability to depart Genesis with Blue Team. With the aid of Exuberant Witness, Osiris is successful in preventing Blue Team’s departure. Meanwhile, Artificial Intelligence beings throughout the galaxy swear allegiance to Cortana, plunging Earth and other colonies into the dark age with the Guardians’ EMP strikes. The Infinity commits to random slip-space jumps to avoid a similar fate. With Blue Team recovered, Osiris returns to Sanghelios, reuniting the SPARTAN-IIs with Dr. Halsey. If the player completes the game on Legendary difficulty, an extra cutscene will show an unknown Halo installation seemingly powering up before the cutscene cuts to black.