Fireteam Osiris

"Osiris" redirects here. For the Halo 5: Guardians campaign level, see Osiris (level).

"We are the shield between humankind and danger."

- Spartan Jameson Locke

Fireteam Osiris is a specialized combat and intelligence gathering team of Spartan-IV supersoldiers of the Spartan branch. The team carries out complicated and classified missions for the Unified Earth Government and its United Nations Space Command, typically dealing with issues that are deemed hard to control by the UNSC High Command. Fireteam Osiris' activities are classified at the highest levels of government.

Members
Fireteam Osiris is composed of four of the most prominent and effective personnel from throughout the different branches of the United Nations Space Command. Osiris' members were selected based on their skills, with the desired outcome being that each team member's skills would mitigate another's deficiencies. The fireteam's balanced skillset and impressive success rates causes them to be commonly deployed in extremely sensitive and complex missions.
 * Jameson Locke – Team leader; former acquisitions specialist for the Office of Naval Intelligence.
 * Olympia Vale – Former UNSC Navy intelligence officer and xenoanthropologist.
 * Holly Tanaka – A highly skilled engineer; former member of the UNSC Army Corps of Engineering.
 * Edward Buck – A former Orbital Drop Shock Trooper, and the advisor and mentor of the team.

History
By October, 2558, Fireteam Osiris were assigned to UNSC Infinity.

Rescue and assassination
After several human colonies were unexpectedly attacked by mysterious Forerunner entities, Doctor Catherine Halsey contacted with information about the attacks. In response, Fireteam Osiris were tasked with rescuing Dr. Halsey from the custody of Covenant Supreme Commander Jul 'Mdama on the Forerunner world of Kamchatka.

After being briefed by Captain Thomas Lasky of UNSC Infinity, the Spartans were delivered to Kamchatka via D79-TC Pelican, where they discovered the Covenant engaging their former Promethean allies. Osiris exited the Pelican dropship to free fall past battling Covenant and Promethean ships, using their armor's thrusters to control their following landing. Osiris landed on a mountainside, where the Covenant and Prometheans were currently engaged in combat and the Spartans fought their way through the terrain. While Vale eliminated Covenant forces aboard a Type-57 Phantom, Locke and the rest of Osiris battled numerous Covenant and Promethean forces on the ground. As one of the Covenant blockade runners crashed into a nearby mountain peak, Osiris regrouped and was forced to outrun the ensuring avalanche. The Spartans leaped off a cliff and slide down the mountainside, where they promptly engaged nearby Covenant forces in a valley. With 'Mdama and Halsey located in a nearby Forerunner structure, Fireteam Osiris fought their way past Covenant and Promethean forces to reach their targets' location. Although 'Mdama had a Kraken deployed to fend off the hostile forces assaulting his location, the Prometheans managed to force the walker to retreat.

As Osiris battled their way to the structure, they arrived at 'Mdama's and Halsey's position on a balcony. While Tanaka, Vale, and Buck engaged 'Mdama's Zealot guards, Locke charged towards 'Mdama to begin engaging the Supreme Commander in close-quarters combat. After a brief fight, Locke managed to assassinate 'Mdama, and Tanaka, Vale, and Buck quickly eliminated the remaining Sangheili soldiers on the platform. With Halsey recovered, Osiris and the doctor returned to UNSC Infinity.

Hunting the legend
"Locke"

- The Master Chief

Upon their return to Infinity, Fireteam Osiris learned that Spartan-IIs John-117, Kelly-087, Linda-058, and Fred-104 of Blue Team traveled to the Outer Colony of Meridian—absent without leave—to investigate smart AI Cortana's location. Osiris was tasked with embarking to the recently resettled and now independent Meridian to track down Blue Team and take them back to the UNSC. To prepare for the mission, Locke tasked an AI to identify weaknesses in Spartan-IIs and the MJOLNIR Mark VI and acquired armor-locking device in order to short circuit their armor's systems. Fireteam Osiris arrived at Pinnacle Station—the Meridian space elevator—via Pelican, where they descended to the moon's surface. Osiris quickly discovered that the world was also under attack from Promethean constructs and Meridian's settlers were desperately attempting to fend off the invaders. In exchange for colony leader Governor Sloan's cooperation, Osiris agreed to help defend Meridian from the Prometheans. After destroying the Prometheans that were assaulting the outpost at the space elevator's base, the Spartans began travelling to Meridian Station, the lead settlement on the moon which the Prometheans were attempting to invade. However, Sloan was reluctant to give Osiris access to the road leading to the settlement, fearing that the Prometheans would follow. However, Osiris eliminated the surrounding Prometheans and Sloan allowed the Spartans to have access to the road. At Sloan's request, Osiris aided several settlers under attack at a nearby service garage and Sloan ordered his men to give the Spartans one of the Liang Dortmund Corporation's M820 Scorpions to use against the Prometheans in exchange for their help.

After using the Scorpion to clear out the rest of the nearby Prometheans, Vale and the rest of Osiris proceeded to Meridian Station, where they discovered that Sloan was a smart AI suffering from onset rampancy. Sloan allowed the Spartans to search the settlement for clues about Blue Team's location, leading to Locke having Osiris split up to see if they could learn anything from the local settlers. After learning that Blue Team's prowler was seen traveling to the nearby Apogee Station, Fireteam Osiris boarded a transport Pelican and departed for the settlement. Upon arriving at Apogee, they found the settlement under attack. Working with Meridian soldiers, Locke and the rest of the Spartans cleared out the Prometheans and discovered Blue Team's abandoned prowler. Accessing the prowler's data banks, Osiris discovered that Blue Team had traveled to the mines under the settlement. After eliminating more Prometheans throughout the mines, Osiris discovered that the Meridian settlers had found a massive Forerunner structure underneath the moon's surface. As they investigated the structure, they eventually came across the Warden Eternal, an ancilla that served as the protector of the Forerunner Domain and claimed his loyalty belonged to Cortana. After refusing to allow the Spartans to pursue Blue Team, Fireteam Osiris engaged the Warden and eventually destroyed him. Advancing forward, Osiris came across a Guardian in a large, cavernous chamber. While exploring the area, Vale discovered a local slipspace translocation network throughout the cavern and noticed Blue Team using it on above platforms. Following Vale, Locke and the rest of Osiris pursued Blue Team as they advanced from platform to platform utilizing the translocation network. During the chase, Locke got ahead of the rest of his fireteam and was teleported to the same platform that Blue Team was on.

As the Spartan-IIs prepared to travel through one last teleporter to reach the Guardian, Locke ordered them to stand down. The rest of Osiris was teleported to a higher platform, as John-117 ordered his own teammates to go through the portal ahead of him. When John refused to stand down and moved to follow his team, Locke attempted to detain him, leading to a hand-to-hand combat fight between the two while the rest of Osiris watched nearby. John eventually gained the upper hand and used Locke's own armor restraint against him. As John escaped through the portal and entered the Guardian, the massive construct began to activate and the floating platforms around Osiris began falling out of place and into the lava below. Freeing Locke, the four Spartans rushed back the way Blue Team came by traveling back to each platform via teleporter. Fireteam Osiris was just able to enter the last teleporter as its platform plummeted towards the lava, with Locke assisting Buck through the portal when the latter had nearly fallen off the platform. The Spartans were teleported back to Meridian's surface, where they discovered that the colony was already well into its evacuation as settlers rushed into the moon's space elevator. As Osiris raced to the elevator to escape the ensuring damages that would be caused by the Guardian's activation, the construct rose out of the surface nearby. After fighting their way to the base of the elevator, Sloan allowed Osiris to enter. Sloan then revealed that he was warned of the Guardian's activation by Cortana, and that he intended to be a part of the future Cortana was creating for humans and AIs. Osiris destroyed the remaining Prometheans nearby and, after activating it, the fireteam began ascending the space tether. On the way to the elevator terminal, while engaging more Prometheans, the Guardian sent out a shockwave that heavy damaged the elevator. The Spartans were forced to climb the elevator as the structure slowly began to fall. Just as Osiris arrived at the platform their Pelican was on, the Guardian continued to send out more frequent shockwaves that slowed the Spartans down and caused the platform they were on to collapse. Osiris barely managed to enter the dropship, with Locke having to use his armor thrusters to board the Pelican as it fell from the platform. Once Locke was aboard, the Spartans left Meridian's atmosphere as the Guardian entered slipspace and left the moon.

Alliance on Sanghelios
"Buck"

- Locke

After Fireteam Osiris returned to Infinity, Lasky ordered for the fireteam—along with Commander Sarah Palmer and Halsey—to travel to the Sangheili homeworld of Sanghelios to utilize the planet's inactivate Guardian to pursue Blue Team. Vale and the rest of Osiris were taken to the planet's surface via Type-56 Lich, where they were tasked with finding Arbiter Thel 'Vadam while he was leading the Swords of Sanghelios against the invading remnants of 'Mdama's Covenant at the Elder Council Chamber in Nuusra. As Osiris engaged Covenant forces, Palmer had Mahkee 'Chava deploy two Mantises for the Spartans to utilize in clearing out the Covenant warriors at the Elder Council Chamber. Upon arriving at the chamber, Osiris battled the Covenant forces assaulting the building and fought their way inside, where they meet up with 'Vadam. With Osiris' help, the Swords of Sanghelios eliminated the Covenant forces at the Council Chamber. Moments later, 'Chava arrived in a Phantom and extracted the Arbiter and Spartans. Traveling to the Swords of Sanghelios' encampment at Nuusra, Osiris worked together with Halsey, Palmer, and 'Vadam to formulate a plan to utilize the Guardian. 'Vadam, recognizing Locke as the ONI agent that had planned to assassinate him in the Covenant War, was initially reluctant to move his forces to assist the Spartans. However, when Cortana briefly shorted out all electronics at the encampment, 'Vadam agreed to work with Locke. Osiris was tasked with locating a Forerunner Constructor at one of the Guardian's nearby support stations to allow Halsey to input commands into the construct to force it to activate the Guardian. Palmer flew Fireteam Osiris to the support station, but was forced to drop them off just south of the facility due to the presence of a Covenant Kraken nearby. While the Spartans provided ground support, the Swords of Sanghelios assaulted the walker from the air. While the Arbiter's flight squadrons forced the Kraken into retreat, Osiris fought their way to an ancient Sangheili temple located near the support facility. After defeating several Prometheans at the temple, the Kraken arrived at the temple, threatening Osiris' mission. As the walker neared, the Spartans boarded the Kraken and destroyed its power generator from within. Osiris fled that doomed walker and traveled into the support facility via stolen Type-54 Banshees. Once inside the station, Osiris retrieved a Constructor, but were attacked by Promethean forces. After battling their way back to an extraction point with the Constructor, a Phantom transported them back to the Swords of Sanghelios' encampment.

With the Constructor, Halsey inputted her commands into it and the construct took off to activate the Guardian. However, the Guardian was located in the Csurdon Sea next to the city of Sunaion, the last bastion of the Covenant on Sanghelios. The Arbiter's forces regrouped and prepared to attack the city to eliminate the Covenant and give Osiris a chance to board the Guardian. Traveling to Sunaion with a squadron of air vehicles, Fireteam Osiris, Arbiter 'Vadam, and several Swords of Sanghelios forces were deployed to Sunaion and engaged Covenant soldiers throughout. While the Arbiter led his forces against the Covenant directly, Osiris destroyed Covenant anti-air emplacements to allow the Arbiter's fleet to move in closer to the city. Unable to receive air support for transport to the Guardian, Osiris accessed Sunaion's undercity to travel to its location. When the Constructor activated the Guardian, Promethean forces arrived at the battle and began engaging the Spartans, as well as the Arbiter and his forces. When the Guardian began rising out of the sea nearby and started to activate its shockwaves, the buildings around the Spartans were ripped apart. As the Spartans moved to safety, they regrouped with the Arbiter as he was engaging Promethean forces. The five battled the onslaught of Prometheans, which were soon led by the Warden Eternal, now utilizing another physical body. After a lengthy engagement, the five destroyed the Warden and the nearby Prometheans just as the Guardian prepared to leave. While the Arbiter remained behind to finish eliminating Covenant and Promethean forces, Palmer and Halsey picked up Osiris in the Pelican and flew towards the Guardian. A pursuing Banshee damaged the dropship, though Palmer was still able to drop Osiris off on the Guardian's surface just as it entered slipspace and left Sanghelios.

Trivia
Osiris was an Egyptian god of the afterlife, the underworld, and the dead.

Production notes

 * Fireteam Osiris is featured in Halo 5: Guardians. They accompany Locke throughout the campaign and accept commands from the player. Buck, Tanaka, and Vale are playable in cooperative play, each with a specialized default loadout. The team has access to the Artemis Tracking System which can highlight alternate routes as well as various items of interest.
 * Buck's place as the fourth member of Fireteam Osiris was filled by Gabriel Thorne in an early phase of the development of Halo 5: Guardians. Due to Ethan Peck being preoccupied with another television series, Thorne was replaced by Buck later on after Nathan Fillion agreed to reprise his role. Thorne is still shown alongside the members of Osiris in an early piece of artwork featured as the cover of The Art of Halo 5: Guardians.

List of appearances

 * Halo 2: Anniversary
 * Halo: New Blood
 * Hunt the Truth
 * The Hunt Begins
 * Halo 5: Guardians
 * Limited Edition