When Blue Team goes absent without leave to track down the artificial intelligence construct Cortana, Master Chief's loyalty is called into question and Fireteam Osiris is sent to retrieve him.

Upon release, Halo 5 received positive reviews from critics, with praise directed at its gameplay, visuals, level design and multiplayer modes.

[1] Players assume the role of powerful "Spartan" supersoldiers with a host of abilities, and use on a combination of guns, grenades, and melee attacks in story-based campaign and multiplayer modes.

[7] Players can control computer-controlled fireteam members with simple directions via the d-pad; for example, picking up a weapon, getting into a vehicle, or prioritizing a selected enemy.

Blue Team is led by Master Chief Petty Officer John-117 and is composed of his fellow Spartan-II supersoldiers:[17] Linda-058, an elite sniper; Kelly-087, a scout; and Frederic-104, a hand-to-hand combat specialist.

[21] Fireteam Osiris is deployed to the planet Kamchatka, occupied by Jul 'Mdama's faction, to retrieve Halsey amidst a battle between Covenant forces and Forerunner Prometheans.

Captain Lasky declares Blue Team AWOL; Halsey believes that Cortana's survival through the use of Forerunner technology makes her unpredictable and untrustworthy.

Chief bests Locke in hand-to-hand combat and Blue Team boards a Guardian, a colossal Forerunner construct built as planetary enforcers.

Osiris barely escape the colony's collapse as the Guardian activates and teleports away to the Forerunner planet Genesis, where John and Cortana reunite.

Longo and game leads David Berger and Chris Lee laid out the studio's vision for the next game from a creative and technical standpoint, setting key goals to focus on: utilizing the Xbox One's hardware and Microsoft's cloud infrastructure for larger campaign and multiplayer spaces, deeper player investment systems, and a 60 frames per second (FPS) frame rate.

The narrative team decided Smith would be a former intelligence agent, a cross of James Bond and Lara Croft, while the still-unnamed Jones (later Vesper) would be an expert in alien languages.

When Thorne's voice actor, Ethan Peck, was unavailable due to scheduling conflicts, 343 Industries decided to replace his character on the team roster rather than recast the role.

[32][33] Eager to take advantage of the hardware, the art team built fully animated cacti that responded to gunfire, blanketing the campaign maps with the succulents.

Bouvier described the early stages of developing artistic concepts as akin to sculpting from marble: "[we] start with a very loose idea that has trickled down from the writers or studio creative director and begin chipping away at the problem."

"If there's no plausible story behind something, it shouldn't be there," he said, recalling that an original plan for a fountain on the mining world of Meridian was changed to a holographic tree, to reflect the desire to simulate nature in the barren landscape.

[41] Holmes stated that the development team wanted Halo 5's multiplayer to provide gameplay variety and support different play styles.

[43] Warzone, one of the new multiplayer modes, was originally conceived in 2012 with a small demo set up as a four-versus-four player match with AI controlled enemies defending an objective.

[45] After E3, Xbox executive Phil Spencer said the previously announced "Reclaimer Trilogy", of which Halo 4 had been the first entry, had been expanded into a larger saga, explaining that the developers did not want to limit the story to just three games.

[52] The development team wanted to launch a beta as early as possible so that players could give feedback,[24] which was used to make refinements to gameplay and adjustments to maps.

[65] The first season was highly successful, drawing an audience of 6.7 million listeners on iTunes and winning Hunt the Truth's ad agency a Clio Award.

[66] A second season of the podcast began September 22, 2015, focusing upon the view point of ONI Agent Maya Sankar (Janina Gavankar), returning undercover as FERO, to investigate unidentified attacks on human colonies.

The limited edition came with a REQ bundle, dossiers on the game's characters, the Fall of Reach film, a statue of a Guardian, and a "steelbook" metal case.

[90][6] Destructoid's Chris Carter felt that Halo 5 failed to grab him in the same way as previous games had, "but those of you who are still content with Master Chief and his wacky adventures across the galaxy will likely walk away satisfied.

"[97] GameSpot's Mike Mahardy felt that while the plot had promise, the campaign did not effectively capitalize on its opportunities: "Cutscenes fade to black before they feel finished.

"[90] Forbes' Paul Thier and GamesRadar's David Houghton complained that players did not suitably impact the story's progression, and that the game's cliffhanger ended the plot at the conclusion of the first act.

[98][99] Though he also found fault with parts of Halo 5's campaign, Albert praised Cortana's threat as "less black and white" in motives than previous antagonists, and the background chatter contributing to learning more about each character.

[100][101] Phil Hornshaw of Digital Trends wrote that Halo 5's marketing "suggests an emotional conflict between the questionably-loyal Chief and the 'traitor-hunting' Osiris leader, Locke, but those moments are barely in the game".

[105][106] Within its first five days of release, Halo 5 was the best-selling game of October in the United States, according to NPD Group,[107] which tracks physical sales from retailers.

[110] In the United Kingdom, Halo 5 debuted on the top of the sales charts as measured by Chart-Track, besting the week's other new release, Assassin's Creed Syndicate.

[111][112] The following week sales decreased 78 percent, and Halo 5 was displaced from the top of the charts by Call of Duty: Black Ops III.