Battle of Nuusra

"With Arbiter's victories and the death of Jul 'Mdama, the Covenant grow desperate. They have began an assault on 'Vadam lands, targeting Arbiter specifically."

- Mahkee 'Chava to Fireteam Osiris.

The Battle of Nuusra was a conflict between the remnants of Jul 'Mdama's Covenant, the Swords of Sanghelios (aided by UNSC forces), and Promethean forces on October 27, 2558.

Global war
Murok 'Vadam would give up information as to where the Arbiter was to the Covenant. In exchange, the Covenant promised him power and prestige.

Rescuing the Arbiter
"Secure the area! Kill every Sword of Sanghelios you see! We will not let the false Arbiter escape this time! For the Covenant!"

- A Covenant soldier to other troops.

With the UNSC needing to access to the Guardian at Sunaion, Fireteam Osiris was deployed to Nuusra to meet up with Arbiter Thel 'Vadam. In the morning of October 27, 2558, the remnants of Jul 'Mdama's Covenant invaded Nuusra in an attempt to assassinate 'Vadam who became cornered in the Elder Council Chamber. Deployed by Phantom into the region, Osiris fought their way towards the Council Chamber, aided by Mantises dropped by Shipmaster Mahkee 'Chava and several Sangheili Storm. Finally, as the Arbiter was about to be overrun, Osiris and their Sangheili allies reached the Elder Council Chamber and extracted the Arbiter by Phantom.

Regrouping
"Jameson Locke"

After the initial fight, Spartan Jameson Locke brought up the need to access the Guardian at Sunaion, but as it was the last Covenant stronghold on the planet, the Arbiter refused to commit his forces until they could be sure of victory. Dr. Catherine Halsey determined that using a Forerunner called a Constructor, she could interface with the Guardian and activate it. As Nuusra was filled with support facilities for the Guardian, it would be relatively simple to find one. Fireteam Osiris was redeployed by Pelican to visit one such facility with the Swords of Sanghelios for backup. The Arbiter saw the launch of the Guardian as a chance to crush the Covenant once and for all using the distraction the Covenant soldiers would experience upon the Guardian's launch.

Retrieving the Constructor
"Osiris, Halsey's Constructor is in a Forerunner facility north of here, but the Covies have a Kraken parked between you and it. Arbiter's people are set to hit the Kraken from the air while you handle ground support."

- Spartan Commander Sarah Palmer to Fireteam Osiris.

Fireteam Osiris is deployed by Pelican south of the Forerunner facility containing the needed Constructor. With a Covenant Kraken and ground troops blocking the way, the Arbiter deploys Banshees to handle the Kraken while Osiris is left to handle the ground troops. Fighting through the area, Osiris encounters a shielded entrance that they have to bypass. Eventually, the Covenant Kraken and airborne forces begin abandoning their ground forces which retreat into the temple grounds which are between Osiris and the Forerunner facility. In the temple ruins, Osiris encounters another shielded entrance, with the ground forces supported by a Wraith dropped by a Phantom.

Reaching the end of the temple ruins, Osiris discovers a canyon with the Forerunner facility on the other side. However, the retreating Kraken enters the canyon and ends up between the Spartans and the Forerunner facility. Spotting nearby Phaetons, Osiris decides to help the Arbiter finish off the Kraken and the remaining Covenant forces in Nuusra. Using the Phaetons, the Spartans take out the defenses on the Kraken's main platform and land to assault the power core. Making their way to the Kraken's lowest level, Osiris fires on the power core until it overloads and explodes, and then flees in Banshees. Losing power, the Kraken falls to its demise in the chasm below, taking with it the remaining Covenant forces.

With the Covenant forces cleared out, Osiris enters the Forerunner structure and attracts a Constructor's attention by damaging a Forerunner terminal. However, the attack also draw the attention of Promethean Knights, Watchers and Soldiers. Osiris clears out the Promethean attackers and, along with their captured Constructor, are extracted by a Swords of Sanghelios Phantom.

Aftermath
"Today the Covenant will fall! Sanghelios will be free!"

- Arbiter Thel 'Vadam to his forces prior to leaving for Sunaion.

With the Constructor in their possession, the UNSC and Swords of Sanghelios forces begin planning their assault on the final Covenant stronghold at Sunaion where the Guardian is. Dr. Catherine Halsey programs the Constructor to use the recording from the Meridian Guardian to activate the Guardian and travel to where the other Guardian took Blue Team. Though the Constructor is expected to take hours to days to be ready, the Forerunner device is prepared faster than expected.

Roughly around the same time, Security officer Mahlo 'Turagg eventually manages to convince a Covenant Unggoy to reveal that the Covenant were able to locate the Arbiter at the Elder Council Chambers thanks to Murok 'Vadam of the Arbiter's own keep. Murok does not resist questioning, perhaps believing that the Arbiter would not execute a member of his own clan. However, this belief is incorrect, as the Arbiter executes Murok for his treason.

With everything ready, Fireteam Osiris and the Swords of Sanghelios set out to launch the Guardian and take down the Covenant once and for all. Working together, Fireteam Osiris and the Swords of Sanghelios are able to crush the Covenant forces at Sunaion and Osiris uses the Guardian to reach Genesis.

List of appearances

 * Halo 5: Guardians
 * Halo: Legacy of Onyx