Thel 'Vadam

"Were it so easy."

- Common expression used by Thel 'Vadam

Thel 'Vadam (formerly 'Vadamee) is the Sangheili Kaidon of the Vadam family. He was the last Arbiter to serve the Covenant, and continued to be widely known by his title in the closing months of the Human-Covenant War and in the post-war period. Thel commanded numerous fleets during his service in the Covenant, most notably as the Supreme Commander of the Fleet of Particular Justice, which mounted a successful invasion and occupation of the human colony Reach and later during operations on Installation 04.

During the Great Schism, Thel became a leading member of the Covenant separatists, and aided the UNSC in their effort to stop the Prophet of Truth and his forces from activating the Halo Array. He fought many battles alongside the "demon" John-117 on Installation 05, Earth, and Installation 00 in the final days of the war.

Returning to Sanghelios after the conclusion of the war, the Arbiter went on to become a symbol of Sangheili honor and resilience in the face of betrayal. He attempted to unite the feudal states across his homeworld in forming the first coalition government since the First Age of Conflict. Despite his efforts, he met resistance from many of his people, who felt that his ideals and beliefs went against the traditional values of the Sangheili.

Early life
Thel was born to the Vadam family, rulers of the powerful state of Vadam on Sanghelios. In his youth Thel was trained in the ways of fighting by his relative Lak 'Vadamee. He later joined the Covenant military, adding the "-ee" suffix to his surname according to custom. Thel participated in the Covenant attack on the human colony Madrigal in 2528.

Within a short time, Thel achieved both the rank of Zealot and the title of Shipmaster, and became Kaidon of his state through the votes of Vadam's elders. Shortly after being promoted to Shipmaster, Thel sustained an injury in the training ring due to a mistake. His family hushed up the incident, as well as the resultant visit by a physician, due to the Sangheili's cultural stigma toward doctors and medical operations. During his convalescence, Thel handmade an old-fashioned doarmir-fur Shipmaster's cloak, and would later wear it as part of his Shipmaster's attire to remind him that he could make grave mistakes if he let his guard down.

Life as Kaidon
"It is a poor soldier who insists on seeing things not as they are, but as he wants them to be. One day reality hits, and his illusions fail him, and he dies stupidly. What honor is there in that?"

- Thel 'Vadamee

Thel's role as Kaidon was important for the Vadam family, as he was tasked with continuing the reign of the powerful state of Vadam. Early in his rule, he was attacked by three Sangheili assassins wielding Energy Swords. He managed to kill all three without injury, and proceeded to appear before Vadam's elders to determine which had ordered the attack. Thel discovered that the assassination orders had come from the elder Koida 'Vadam, and after killing him, he ordered all of Koida's line to leave Vadam keep by sunrise.

Thel was sent to Charybdis IX with command over the vessel Retribution's Thunder to participate in the Battle of Charybdis IX, while being overseen by the High Prophet of Regret. He and several other Sangheili boarded the and attempted to access the vessel's navigation database, but it had already been purged. He left and witnessed the destruction of the ship before being called to the Infinite Sacrifice, where he met the Prophet of Regret in person. Regret informed him of humans reportedly wielding modified Covenant weapons, a transgression he believed to be the doing of the Kig-Yar. He was then sent to the 23 Librae system to track down the source of the illegal weapons traders. For the mission, his ship was accompanied by the Kig-Yar vessel A Psalm Every Day, commanded by Shipmistress Chur-R 'Mut and the Jiralhanae Chieftain Pellius.

Upon arriving at 23 Librae, Thel and his crew discovered the Rubble, a collection of asteroid habitats built by Kig-Yar and Insurrectionist humans working together. Almost immediately afterward, the Thunder was attacked by A Psalm Every Day; Pellius had decided to betray Thel so that he could claim sole credit for the discovery. Thel and his crew were taken by surprise, allowing the traitorous vessel's second salvo to disable the Thunder's weapons, communications and engines. A Psalm Every Day escaped while Kig-yar boarding craft and Spirits strafed the hull. Thel, increasingly frustrated, gave permission for his crew to abandon ship; this was a test to weed out the weaker Sangheili among his crew. Enemy Spirits destroyed the retreating craft in short order. Thel then ordered the destruction of the Retribution's Thunder, which killed the boarding Kig-yar. Thel, however, survived and was captured, imprisoned on the Rubble along with most of the bridge crew. They ultimately managed to escape and hijack a Kig-yar shuttle, taking them to another Kig-yar vessel. On the surface of Metisette, Thel captured the leader of the warband, Reth.

Escaping Reth's clandestine Unggoy army, Thel returned to the Kig-yar's vessel. Throughout the interrogation, the Sangheili were surprised by Reth's insistence that he was allying with the humans with the blessing of the High Prophet of Truth. According to Reth, the sale of the contraband weapons was a bluff in order to locate human worlds through tracking devices implanted in the weapons. Reth eventually escaped when a loyal grunt switched off his prison's energy barrier, fleeing via escape pod. Thel then turned his eyes to the Rubble, as a large skirmish between UNSC forces and Kig-yar forces was taking place on the Infinite Spoils. The Sangheili and his crew boarded the Infinite Spoils and came face to face with Jai-006, engaging him in a brief fight. The Spartan then fled the ship with the other UNSC forces. Thel, surprised at the strength of the human warrior, stayed behind and commandeered the Infinite Spoils.

Thel managed to destroy most of the Rubble's mass drivers, but was left helpless when The Redoubt was destroyed and Habitat Exodus left the system. There was little else to do but wait for the High Prophets of Truth and Regret to arrive and recover him with his comrade, Zhar. Upon reporting the failure of the mission, Zhar attempted to kill the Prophets feeling helpless at the loss of his honor caused by the Prophet's scheming. Thel activated his Energy Sword and killed his friend without mercy. This act prompted Truth to spare his life, and he gave Thel command over a ship in the Fleet of Particular Justice.

Life as Supreme Commander
"Soon the Great Journey will begin, but when it does, the weight of your heresy will stay your feet, and you shall be left behind."

- The Prophet of Truth to 'Thel Vadamee at his hearing.



At some point between 2535 and 2552, Thel's exceptional leadership and combat prowess earned him the rank of Supreme Commander of the Fleet of Particular Justice. Near the end of his time serving as Supreme Commander, he led the Covenant forces under his command to victory over the UNSC's greatest military stronghold. The Fall of Reach proved to be the highlight of Thel's service in the Covenant. As the battle ended, Thel ordered a flotilla of warships to follow the fleeing UNSC Pillar of Autumn. The Autumn's course led them to holy Forerunner artifact Installation 04. After confirming that the ring was a creation of the "gods", the Prophet of Stewardship, the highest ranking political figure with the Fleet, immediately claimed authority over the operation, claiming the mission was now a religious matter. As Thel was unwilling to relinquish command with the Pillar of Autumn en route, and unable to contact High Charity to determine who held jurisdiction, a power struggle emerged between Thel and Stewardship for ultimate authority. As the Battle of Installation 04 wore on, the Prophet began subverting Thel, misappropriating military forces to secure facilities on the ring. Thel sent a single infantry unit to the Ascendant Justice to relieve the Prophet, but it was destroyed on approach. Stewardship threatened further punishment for any future affronts to his leadership. As Thel assembled a strike force to physically relieve the Prophet, the emergency beacon on the Infinite Succor was activated. Thel dispatched a Special Operations force to assess the threat and procure the Minister of Etiology. As Thel was about to leave with his strike force for Ascendant Justice, Spec Ops Commander Rtas 'Vadumee returned to the ship and revealed the results of his mission: the Flood had been unleashed on Halo. With the situation deteriorating, Thel ordered the evacuation of all ships from the ring, as well as shooting down any vessel which failed to return clean bioscans. When Thel's force arrived on Ascendant Justice, he discovered that the Prophet of Stewardship had left for the Truth and Reconciliation. The crew of the Ascendant Justice acknowledged Thel's authority as Supreme Commander without hesitation. Unsurprisingly, Thel refused to come to the Steward's aid after its capture by the UNSC. These distractions were to cost Thel the battle, as SPARTAN-117 and Cortana successfully detonated, Pillar of Autumn under the nose of the Covenant's occupation. With little else to be done, Thel ordered his surviving ships to fall back. This retreat was to save his life, but not his honor. In an act that further humilated Thel, the Ascendant Justice was captured by John-117 and a small human boarding party. Shortly after his ships failed to pursue the Ascendant Justice, Thel was called before the Covenant High Council to answer for his failures.

The loss of the holy Forerunner relic was an unforgivable failure in the eyes of the High Prophets and Sangheili Councilors. 'Vadamee was stripped of his rank, title, name, and honor, and branded a heretic for his failure to safeguard the Sacred Ring. The Mark of Shame was branded upon his chest, and he was sentenced to death. His corpse was to "be hung by his entrails" and "paraded through the city" as an example to others.

The Hierarchs, however, had a different fate in mind for Thel. Upon being brought before the Prophets of Truth and Mercy, Thel was offered the choice of becoming the new Arbiter. Understanding that the office of Arbiter was itself a death sentence and seeking to regain his honor, Thel accepted.

Threshold gas mine


"What would you have your Arbiter do?"

- 'Vadamee to the Prophets

'Vadamee's first assignment as the Arbiter was to stop the Heretic uprising based on a Forerunner gas mine in the atmosphere of Threshold. He was assisted by Rtas 'Vadumee, Special Operations Elites, and Special Operations Grunts. The operation was complicated by the unexpected escape of the Flood from the facility. During the chaos that followed, the Heretic leader Sesa 'Refumee sealed himself in a protected zone of the station. The Arbiter drove the Heretics out by cutting the cables from which the facility hung, causing the gas mine to fall. After crashing his Banshee, the Arbiter fought his way through the Flood and surviving Heretics toward the station's hangar. Before Sesa 'Refumee could escape in a Seraph, the Arbiter assassinated him, but not before the Heretic Leader revealed the source of his heresy. The Arbiter was surprised to discover that the Heretics had been aided by a Holy Oracle, the Monitor 343 Guilty Spark.

With the uprising suppressed, the Brute Chieftain Tartarus extracted the Arbiter and used the Fist of Rukt to capture the Oracle. His actions, which involved throwing the Oracle into the Phantom recklessly, angered the Arbiter's religious sensibilities. With Tartarus, he left the gas mine via Phantom, as High Charity and the fleet departed the Threshold system.

Battle of the Quarantine Zone
"We shall cut into the heart of this infestation, retrieve the Icon, and burn any Flood that stand in our way!"

- Rtas 'Vadumee



The High Prophets, surprised by the fact that 'Vadamee had escaped from the gas mine, decided to send him to the "Quarantine Zone" on Installation 05 to retrieve the "Sacred Icon". This holy relic was needed to activate Delta Halo and begin the Great Journey. Before the mission, the Arbiter witnessed the replacement of the Elite Honor Guards with Brute Honor Guards as a result of Regret's assassination at the hands of the human Demon. Though distressed by change, and voicing his concerns to the Prophet of Truth, 'Vadamee made no further comment. Fighting his way through the Sentinel Wall (with a few surviving Grunts and Jackals) to deactivate the Library's quarantine shield, he made his way on foot, aided by Rtas 'Vadumee and his Special Operations forces.

The Arbiter proceeded into the Library, encountering the remains of a battle between UNSC Marines, Sentinels and Flood combat forms, and witnessed Commander Miranda Keyes and Sergeant Johnson retrieving the Index. Using his armor's active camouflage, he approached Johnson and Keyes. Attacking while cloaked, 'Vadamee surprised Johnson, knocking him unconscious with a headbutt. Keyes attempted to shoot Thel, but was quickly disarmed and captured. Tartarus then arrived and captured Keyes by using his hammer's gravity manipulation abilities, claiming the Index for himself. Tartarus informed Thel about the Brutes' intended genocide of the increasingly incompetent Elites, an act sanctioned by the High Prophets themselves. The Chieftain then knocked the stunned Arbiter into a pit leading to the depths of Installation 05.

Control room of Installation 05
"This one is but flesh and faith, and is the more deluded."

- The Gravemind describing Thel 'Vadam

The Arbiter was rescued from his fall by the Gravemind, the central intelligence of the Flood, and brought to its lair. It was here that the Arbiter met John-117 for the first time. The Gravemind attempted to convince 'Vadamee that the Halos were weapons of destruction, not a path to transcendence, a position which John supported. In order to "show the truth" to the resistant Arbiter, the Gravemind teleported him to the Control Room, while the Master Chief was sent to High Charity to stop the Index from activating Halo.

Observing first hand the results of the Prophets' betrayal, the Arbiter joined forces with a band of Special Operations Commandos. This small unit wasted little time in massacring the Brutes responsible for executing the Sangheili's Councilors. Eventually, Thel met Rtas 'Vadumee, joining forces to reach a Scarab. Near the Scarab, the Arbiter managed to rescue several separatist prisoners, as well as a group of UNSC Marines including Sergeant Avery Johnson.

Johnson negotiated a tenuous alliance with the Arbiter in order to prevent Tartarus from activating Installation 05. Given the extreme danger posed by the ring, they both agreed that Tartarus had to be stopped at all costs. Johnson led the offensive, using a captured Scarab to eliminate ground units while Thel provided air support with a Banshee. Together, they punched a hole through loyalist lines and reached the Control Room of Installation 05.

Battle with Tartarus
"Tartarus, the Prophets have betrayed us."

- Thel 'Vadamee's last attempt to convince the Brutes of the truth

'Vadamee fought several Honor Guard Brutes before facing Tartarus, who had forced Miranda Keyes to activate Installation 05. Attempting to open Tartarus' eyes, Thel asked 343 Guilty Spark what Halo's true purpose was. The Monitor replied that the Halos were built "to destroy all sentient life within three radii of the galactic core," as a weapon of last resort against the Flood. The Forerunners had not transcended into gods, but rather died as a final sacrifice to ensure the defeat of the ancient parasite.

With this revelation, the Arbiter attempted to convince Tartarus to see reason. The Chieftain however, remained loyal to the Prophets. In the battle that followed, the Installation was activated. With the firing process enabled, the Arbiter, with sniper support from Johnson killed Tartarus after a prolonged firefight. Miranda Keyes then rushed to remove the Index, preventing the activation of the array. The shutdown, however, activated a fail safe system; the rest of the Halos were set to standby mode, and could only be activated remotely from Installation 00. 'Vadamee then escaped the Flood-infested installation with the surviving humans and Sangheili.

Meeting the Chief on Earth
"Were it so easy."

- Thel 'Vadam tauntingly comments on John-117's apparent ease of overpowering him.

After Tartarus' defeat on Delta Halo, 'Vadamee officially changed his surname to "'Vadam", symbolizing his resignation from the Covenant; the rest of the Elites followed suit.

Upon arriving on Earth with Johnson, 'Vadam and several of his allies discovered the Master Chief's point of impact after his escape from Truth's Dreadnought. When John regained consciousness, he attempted to kill 'Vadam with Johnson's sidearm. Johnson quickly informed the Spartan that the surviving Elites had allied with humanity after the Chief's last encounter with them. The Chief took Johnson's word, and 'Vadam assisted the Master Chief through the jungles near Mount Kilimanjaro, guiding him through the dense forest to the dam site. He then aided the Chief and the other UNSC forces during the defense of Crow's Nest from Truth's forces.

Battle of Voi
"Quickly! Let us find their ship. Make short work of this abomination!"

- The Arbiter on the arrival of the Flood

Thel rejoined John-117 at the docks, shortly after the Master Chief cleared the road to Voi of Covenant loyalists. The two then attacked a section of the Covenant mechanized presence defending the area around the Forerunner Portal. Opening a hole in the Covenant anti-air defenses, Lord Hood's remaining ships assaulted the Prophet of Truth's Forerunner Dreadnought. The airstrike was insufficient to destroy the ancient Keyship, and the activated artifact formed an enormous slipspace portal through which Truth and the Covenant fleet retreated. Before Lord Hood could consolidate the scattered human resistance, a Flood-infested Covenant cruiser transitioned out of Slipspace and crashed into the city, infesting a significant area in and around Voi.

The Arbiter and the Master Chief proceeded to cauterize the local area of the Flood, battling their way to the cruiser to overload the crashed ship's engines and destroy the source of the infestation. They were aided by a handful of surviving Marines and Sangheili Special Operations unit led by Ship Master Rtas 'Vadum. From his newly-arrived Sangheili comrades, 'Vadam learned of the fall of High Charity and how a single cruiser had escaped the station's blockade. The Arbiter assisted the Chief in clearing a path to the crashed cruiser. After the Spartan retrieved Cortana from the wreckage, Rtas 'Vadum's fleet glassed Voi and the surrounding area to prevent the Flood from spreading. Thel proved instrumental in moderating tensions between humanity and Sangheili, as the two races that had only recently been dedicated to each others' destruction. While Rtas 'Vadam callously advocated for the glassing of Earth to contain the Flood, Thel argued for a surgical strike on the landmass surrounding Voi.

Battle of the Ark
"The Prophet will die by my hands - not theirs!"

- The Arbiter on the Flood entrance to the battle



Conferring aboard the Sangheili flagship Shadow of Intent, the allies learned from a message sent by the AI Cortana that the Flood were on their way to Earth. However, she claimed that the Gravemind was unaware of the Portal and that a solution to the Flood was there; one that would eliminate the parasite once and for all without the need to fire the entire Halo Array. Tensions quickly rose with Lord Hood wishing to make the UNSC's stand on Earth, and Thel supporting John's desire to pursue Truth and attack the Flood preemptively.

Arriving at the Ark, the Arbiter joined the Master Chief at the entrance of a local Cartographer facility to clear their way. Once there, they learned of Truth's location, as well as the forces he had deployed to the Ark's surface. When the group was attacked, the Arbiter joined the battle for air superiority, instructing John to follow 343 Guilty Spark to a nearby location for extraction.

With the destruction of the Covenant loyalist fleet, Rtas 'Vadum's carrier positioned itself near the Ark's Citadel - where Truth planned to remotely activate the rings. Commander Keyes led a three-pronged assault on the shield generators protecting Truth's citadel. After Sergeant Major Johnson failed to deactivate the third generator due to heavy resistance, the Arbiter landed his forces at the third tower to deactivate the final generator and shut down the barrier.

As 'Vadum prepared to bomb Truth's position, High Charity exited Slipspace, crashing into the Ark. In its plummet to the surface, High Charity scattered a barrage of infection capsules which crippled the carrier. The Arbiter led his forces in conjunction with the Marines to clear the third tower of Flood, with the Chief's assistance. As a security measure, the Arbiter escorted a distressed 343 Guilty Spark to reconnoiter the damage inflicted to the Ark by the Flood, leaving his Sangheili with the Chief to push on to the Citadel.

Death of Truth
"The Prophet of Truth"

- Thel 'Vadam

After Thel and John entered the Citadel, the Flood Gravemind formed a tentative alliance with them, claiming that it would cooperate with them in order to kill Truth and abort the firing of the Halo Array. Fighting through the remains of Truth's forces, the unlikely comrades stood before the last High Prophet of the Covenant. The Arbiter approached Truth, who had been infected by the Flood and was undergoing mutation. The Gravemind spoke through Truth, informing Truth that he was deluded to think he could achieve godhood. Thel claimed that he would have his vengeance upon a Prophet, not a disease, and killed Truth with his energy sword before he could fully transform. After John deactivated the Halo Array, he and Thel faced the betrayal of the Flood, which now no longer faced any obstacles in killing the two and going on to consume the galaxy.

Destroying the Flood
"This is our fight. And I will see it finished."

- Thel 'Vadam to his fellow Sangheili

After a desperate escape from the Flood, the two soldiers witnessed the construction of a new Installation 04. As the newly created Halo was not linked to the rest of the network, it could be fired safely, destroying every remaining Flood infection form in its radius without harming humanity or the Covenant client races. The Arbiter, Johnson and Rtas 'Vadum evacuated all UNSC and Covenant separatist forces from the Ark while John went to rescue Cortana and retrieve the original Index from High Charity. Thel later arrived on High Charity shortly after John set it to self destruct, using a flamethrower to cover their escape.

The two then escaped on a Pelican dropship, crashing it into Installation 04B; after fighting through numerous Flood forms, they rendezvoused with Sergeant Major Johnson and 343 Guilty Spark at the Control Room. The Monitor betrayed them after realizing that an immediate activation of the incomplete ring would destroy it and damage the Ark. In the battle that followed, the rampant 343 killed Johnson and knocked the Arbiter out of the room. After the destruction of 343, Both Cortana and Thel expressed sorrow over Johnson's death, noting his sacrifice would not be forgotten. John activated Halo, with Thel and Cortana joining him as they escaped the crumbling Halo in a Warthog. They succeeded in reaching the Forward Unto Dawn and escaped the Ark and Halo just before it fired. Before departing to the bridge, Thel and John nodded to each other, a moment of mutual respect between warriors. This would be the last time 'Vadam would see the Chief for several years, as he then exited the hangar, and made his way to the bridge, while Chief and Cortana stayed behind and guided the frigate to its jump point, but the slipspace portal collapsed as Forward Unto Dawn transitioned. The aft end of the ship, with John-117 and Cortana aboard, was sheared off and left adrift in unknown space. The bow section, containing 'Vadam, completed the jump and crash-landed on Earth, where he was rescued. The Covenant Empire had ceased to exist, and Thel began the first steps to his people into a new future.

Leader of the Sangheili
Thel acted as a voice of reform to the Sangheili. Returning to his homeworld, he planned to visit each state to make his case for permanent peace with the humans they had battled for so many years; one of these would be a meeting in the state of Mdama. It was here that he announced that he no longer felt he was an Arbiter, but simply a kaidon. He told the elders that if any of them disagreed with him strongly enough, they could attempt an assassination as per Sangheili tradition.

These reforms did not meet with universal approval. By January 2553, there was great dissent among disparate Sangheili factions, especially from the more devout believers in the Forerunners' divinity. Some, such as Avu Med 'Telcam and his Servants of the Abiding Truth, saw the Arbiter as a traitorous leader that has betrayed their faith and sought to finish their war with humanity. Thel argued with logic, they had not only failed to defeat humanity in the end, but the sundering of the Covenant had left their people without the technical expertise to replace lost warships, or maintain their own infrastructure. In the midst of these events, the Office of Naval Intelligence secretly assisted 'Telcam in creating an insurrection against 'Vadam, in order to keep the Sangheili divided and prevent them from threatening the UNSC.

Cessation of war
"Lord Hood"

- Thel 'Vadam

In February 2553, 'Vadam met with Fleet Admiral Lord Terrence Hood, along with Captain Serin Osman, Corporal Vasily Beloi and Dr. Evan Phillips in the state of Vadam on Sanghelios. There, he and Lord Hood discussed the fragile state of both species, as well as a treaty to formalize the peace. Hood then invited 'Vadam to a memorial service on Earth, and in return 'Vadam invited Dr. Phillips to study Sangheili history and culture on their homeworld.

On March 3, 2553, 'Vadam was present at the dedication of the memorial to those humans lost during the Covenant War. He was thanked by Hood for standing alongside John-117 "to the end"; knowing the resilience of the Spartan first hand, Thel expressed doubt as to the soldier's death. The Arbiter departed for Sanghelios aboard the Shadow of Intent along with Rtas 'Vadum, to ensure the security of their people.

Sangheili civil war
In March 2553, the Arbiter greeted Phillips in Vadam. Phillips requested a tour of Sanghelios' most ancient cities to which Thel approved and assigned Phillips an escort, Cadan 'Ilmir. Not long after, they lost Phillips in Ontom after dissident Jiralhanae detonated an explosive in the state. In the wake of this uprising, 'Telcam and the Servants of the Abiding Truth launched their attack on the state of Vadam. 'Vadam was later contacted by Lord Hood who informed him that he could recover Phillips and quell the rebellion. 'Vadam was doubtful of his offer but graciously accepted his help. Despite 'Telcam's ship having been shot down early in the battle, the situation on Sanghelios intensified as reinforcements from like-minded keeps arrived to attack Vadam keep. Lord Hood arrived on Sanghelios onboard humanity's most powerful ship, the. The Arbiter was caught off guard and as his own reinforcements failed to arrive on time, he reluctantly accepted the UNSC's help in fending off the attackers. Infinity decimated the rebel forces while the posed as a Kig-Yar pirate ship and covertly destroyed some of 'Vadam's ships, leaving the Arbiter with a Pyrrhic victory. After the battle, Thel 'Vadam was in talks to visit the UNSC Infinity.

Peace talks
"The Arbiter. Maybe more than any other figure, a symbol of what the galaxy could one day become."

- Captain Thomas Lasky, before the meeting on Ealen IV.

In 2558, Thel 'Vadam decided to enter into negotiations with the Jiralhanae, with the UNSC Infinity being assigned to escort him. On March 5, 'Vadam met with Lord Hood and the Jiralhanae Chieftain Lydus on Ealen IV. During the negotiations, Covenant mercenaries led by Shipmaster 'Gajat attacked the delegates. Captain Thomas Lasky, Commander Sarah Palmer, and the Spartan-IVs defended the delegation and evacuated them from the chamber. Lydus accused 'Vadam of betraying him, but Thel reassured him that he had no part in the attack as he killed a Kig-Yar sniper attempting to assassinate Lydus. When their evacuation ship was destroyed, the security detail proceeded to escort the delegates to a nearby parts depot.

Inside the repair depot, 'Vadam notified Hood and the rest of an old fortified redoubt in which they could take refuge in. Captain Lasky ordered Palmer and the protection detail to escort the delegation to the redoubt. As the party escaped the depot, they were intercepted by a Covenant Lich. Palmer quickly acted and threw her helmet filled with grenades and destroyed the Lich. The delegation stayed back as Fireteam Jackknife and their bodyguards went ahead to ensure the redoubt was safe for them to use as shelter. However, as the delegates entered the redoubt, Spartan Scruggs of Fireteam Jackknife—who had betrayed his team—ambushed the group and held Hood hostage. 'Vadam queried Scruggs on what his demands were; Scruggs stated that they would discuss them once his associates arrived. With the Covenant bearing on the site in force, the ambassadors' security detail discovered a craft they could use to evacuate. Thanks to the sacrifices of Fireteam Bailey, the delegation, Lasky and the surviving Spartans made it aboard Infinity, which rallied the feuding Sangheili and Jiralhanae fleets and forced 'Gajat's forces into retreat.

Search for John-117
"My friend's trust is not the issue today, Spartan Locke. It is my trust you must earn."

- Thel "Vadam to Agent Jameson Locke.

Thel 'Vadam later met with ONI's Agent Jameson Locke and told him about John-117's past actions and the events yet to come. The Arbiter agreed to aid Locke because both human and Sangheili lives depended on Locke finding the Master Chief.

Personality
Thel, like most Sangheili, held an obsession with honor and tradition for most of his adult life. However, he was more flexible than his peers when it came to the tactics that he used, and in particular showed a keen interest in human weapons even before the Great Schism. His personality changed greatly during the Great Schism. While once zealous and unquestioningly obedient to the Prophets' will, after learning of the true nature of the Halo rings, he became more open-minded and accepting of the humans, his former enemies. His experiences as Arbiter also made him more pragmatic than most Sangheili, being willing to accept help from the UNSC in fending off an assault on his keep.

After the Battle of Installation 04, he was ashamed for his failure at Halo, and wished only regain his honor before dying for the Prophets. After the betrayal of Tartarus and his encounter with the Gravemind, he remained stubbornly attached to his faith. However, when he heard the truth of the sacred rings from 343 Guilty Spark, he finally accepted the truth surrounding the Great Journey.

After Thel was betrayed by the Prophets, he developed an intense hatred of San 'Shyuum. Thel was also one of the comparatively few Sangheili to hold admiration for humanity's courage. This is most clearly seen by his actions to avoid the glassing Earth, even though that meant risking a possible Flood outbreak. He is known to respect Sergeant Johnson and John-117 particularly, despite prior battles, showing genuine grief over Johnson's death and the Spartan's disappearance.

Despite his hatred of the Prophets, Thel was gracious enough to attempt to reason with the Brute Chieftain Tartarus in Installation 05's Control Room. He is shown to be true to his title "Arbiter", and sometimes tries to negotiate with his enemies, such as Drones during the battle of Earth. He holds deep respect for his fellow Sangheili warriors.

Despite his former hatred for humans, Thel has displayed great respect for some, even former battlefield foes. Presumably due to the role Johnson played in his killing of Tartarus, Thel respected him greatly and grieved his death, expressing sorrow to the Master Chief, but promising that his sacrifice wouldn't be in vain. Despite initially hating the Master Chief greatly for destroying Installation 04 and being the "Demon" of the Covenant who killed so many soldiers, the Arbiter came to greatly respect and trust the Chief. The Chief helped convince him of the truth of the Great Journey and they fought together against the Covenant and Truth. Together they defeated Truth and deactivated the Halo Array. When the Master Chief went to rescue Cortana and activate Installation 04B, Thel remained behind to help him and shared a nod of respect with him when it was over. Even though the Master Chief was believed to be dead, Thel showed disbelief in this presumption, confident that the Spartan had survived thanks to his extraordinary ability to overcome impossible odds. After the events of Ealen IV and discovering the Chief was still alive, Thel believed John was the key to the galaxy's future.

Production notes
Voiced by Keith David, the Arbiter was introduced as a secondary playable character in Halo 2; this was part of Bungie's creative decision to broaden the scope of the story from what Jaime Griesemer referred to as an "alien war movie with a space marine". Reception to his inclusion was mixed; Bungie community lead Brian Jarrard attributed some of the fan backlash to a discord between the game's marketing and the actual gameplay; whereas the marketing presented the game's focus as being the defense of Earth from the Covenant, this aspect constitutes only the first missions of the game. In Halo 3, the Arbiter was relegated into a supporting character and there are no levels designed solely from his perspective; he remains a playable character in the co-op campaign.

The original title for the character was "the Dervish", a title from the Sufi sect of Islam, but was changed to avoid overt parallels with the Muslim world. Ultimately, it was decided that "Arbiter" was more thematically suitable for his character arc. In the Spanish versions of Halo 2 and Halo 3, the Arbiter is translated as Inquisidor, which means Inquisitor. This is because the cognate of Arbiter in Spanish, "árbitro", means "referee".

His name, Thel 'Vadam, was first established in the novel Halo: The Cole Protocol. While the narrative does not explicitly connect the character with that of the Arbiter from the games, in the very end of the story a reference is made to him being assigned in command of the Fleet of Particular Justice. It was not until later videos on Halo Waypoint that the Arbiter was explicitly identified as Thel 'Vadam.

In Halo 2 and Halo 2 Anniversary, the Arbiter has no mandible guards, but he does in Halo 3. Notably, the armor of the last known Arbiter, Ripa 'Moramee, did possess mandible guards. In Halo: Escalation, 'Vadam wears a more ornamental, gold-colored suit and overall more closely resembles the Sangheili seen in Halo 4. Unlike in previous media, his now-ashen gray skin has sparse scales instead of being smooth and leathery. He is also depicted with the Halo 4-style mouth structure, such that the bases of his upper mandibles are nearly parallel to his eyes. While his new armor is simply a different suit in-universe, it is unclear whether the changes to his physiology represent a retcon or are simply a case of artistic license. This is particularly notable since Halo 3-style Elites are depicted in Issues 1 and 6.

Trivia

 * When the Arbiter activates his active camouflage in Halo 2, his eyes will remain visible. This is visible only on Co-Op.
 * He is one of the few Sangheili to refer to John-117 as "Spartan". Even during and after the Great Schism, many still refer to him as the Demon (though some, notably, adopt 343 Guilty Spark's designation for him - Reclaimer). Rtas 'Vadum also holds this distinction. Thel has also called him the Master Chief.
 * In Halo 3, if the player outdistances or removes 'Vadam from the map (such as pushing him off a cliff), he will suddenly reappear as if phasing out of Active Camo. This also happens when the Master Chief enters the driver's seat of the Warthog at the end of the level Halo; the Arbiter will appear on the Warthog's turret in this same manner.

List of appearances

 * Halo: The Flood
 * Adjunct
 * Halo: First Strike
 * Halo 2
 * Halo Graphic Novel
 * The Last Voyage of the Infinite Succor
 * Halo 3
 * Halo: The Cole Protocol
 * Halo Wars
 * Halo Legends
 * Origins
 * Halo: Evolutions - Essential Tales of the Halo Universe
 * The Return
 * Wages of Sin
 * From the Office of Dr. William Arthur Iqbal
 * Halo: Glasslands
 * Halo: The Thursday War
 * Halo: Escalation
 * Halo: Mortal Dictata
 * Halo: Broken Circle
 * Halo 2 Anniversary
 * Terminals