Thel 'Vadam

"Were it so easy."

- Common expression used by Thel 'Vadam

Thel 'Vadam (formerly 'Vadamee) is the Sangheili Kaidon of the Vadam family widely known as the Arbiter in the closing months of the Human-Covenant War. Thel commanded numerous fleets during his service in the Covenant Empire, 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. In October 2552, he was stripped of his rank for failing to stop the destruction of Halo; however, at the mercy of the Hierarchs, he was named as the newest, and final, Arbiter to serve the Covenant.

Thel participated in some of the Great War's earliest campaigns in the Outer Colonies, and through his successes, quickly became a Shipmaster. He caught the eye of the Hierarchs after killing a would-be assassin, and was given command of a capital ship. For nearly two decades, Thel would serve in the Fleet of Particular Justice, ultimately rising to become its commander-in-chief. After being branded with the Mark of Shame, he struggled to prove his battle prowess and usefulness as an agent of the Hierarchs. However, he would soon fall victim with the rest of the Sangheili to the treachery of the Jiralhanae. Acting with the Prophet's consent, the Brutes usurped themselves as the new commanders of the Covenant's armies and fleets.

The civil war quickly redefined Thel's loyalties. He would meet and aid, albeit indirectly, the "demon" John-117 against the Covenant and the Flood. Ironically, it was John-117's sabotage of the sacred Halo ring which caused Thel's demotion in the first place. Force to act as a pawn of the Flood Gravemind, he was sent to stop the activation of Installation 05. In the facility's control room, he took his revenge on the Chieftain Tartarus. He proved a vital figure in securing a temporary alliance with the Unified Earth Government. He would prove instrumental in defeating the Covenant loyalists, the Flood, and preventing the activation of the Halo network. The High Prophet of Truth, the sole survivor of the Covenant Hierarchs, would die by his hand in the war's final days. Aiding his former enemy John-117 in deactivating and destroying the Ark, he escaped to Earth by the slimmest of margins.

Back on Sanghelios, the Arbiter would become a symbol of Sangheili honor and resilience in the face of betrayal. Thel would attempt to unite the feudal states across their homeworld in forming the first coalition government since the 1st Age of Conflict. However, many felt his ideals went against the ideals and religion of the Sangheili. Despite being greatly weakened, and in several ways defeated by humanity and the Prophets, many Sangheili retained their desire to eradicate humanity once and for all.

Early life
Thel was born to the Vadam family, rulers of the powerful State of Vadam on Sanghelios. As a young Sangheili, 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 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 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, but he left one alive in order to determine who had ordered the attack. He then killed one of the Vadam elders, Koida, for ordering the assassination, and ordered all of Koida's line to leave the 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, whilst 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, along with the Jiralhanae and Kig-yar vessel, A Psalm Every Day.

As he arrived at 23 Librae, his ship was attacked by A Psalm Every Day. Thel and his crew were taken by surprise, and the vessel's second salvo disabled 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. However, this was a secret test in order to weed out the weaker Sangheili among his crew and eliminate them. 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, 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. The sale of contraband were a bluff in order to location human worlds through tracking devices implanted in the weapons. Reth eventually escaped when a loyal grunt switched off the 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 then 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 gave him 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 of Installation 04. After confirming that the ring 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, and unable to contact High Charity to determine who held jurisdiction, a power struggle emerged between Thel and Steward 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. The Stewart 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, Commander Rtas 'Vadumee returned to the ship and revealed the results of his mission: the Flood was 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. Escaping the flagship before it jumped, Thel was called before the Covenant High Council to answer for his failures.



The loss of the holy Forerunner relic was an unforgivable offense 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 Halo. 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.

Upon being brought to the Prophet Hierarchs of Truth and Mercy, they offered to commute the sentence if he would become the new Arbiter. Understanding that the office of Arbiter was itself a death sentence and seeking to regain his honor, Thel accepted.

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 their agent 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 shield, he made his way on foot, aided by the Spec Ops forces of Rtas 'Vadumee.

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 the Fist of Rukt's gravity manipulation, claiming the Index for himself. Tartarus informed the wounded Arbiter about the Brutes' intended genocide of the increasingly incompetent Elites, an act sanctioned by the High Prophets themselves. Stunned, Tartarus knocked the Arbiter into a pit leading into 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

Narrowly avoiding death, the Arbiter was captured in mid-air 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 'Vadamee, 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 an 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 shaky truce with the Arbiter in order to prevent Tartarus from activating Halo. Given the extreme danger posed by Halo, they both agreed that Tartarus had to be eliminated at all costs. Johnson led the offensive, using a captured Scarab to eliminate ground units while Thel maintained air superiority 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 force Miranda Keyes to activate Installation 05. Attempting to open Tartarus' eyes, the 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

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 M6 Series Magnum. Johnson quickly informed the Spartan that the surviving Elites had allied with humanity after the Battle of Onyx. The Chief took Johnson at his 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 the Crow's Nest from Covenant loyalists.

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

- The Arbiter in Floodgate

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. An enormous, fiery blue sphere was triggered over the activated artifact, and formed a 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. 'Vadam learned of the fall of High Charity and how a single CCS cruiser had escaped the station's blockade. The Arbiter assisted the Chief in clearing a path to the crashed cruiser. Upon completion of the cruiser's destruction, Rtas 'Vadum's fleet glassed Africa to prevent the Flood from spreading.

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

- The Arbiter, in the level The Covenant



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 land mass surrounding Voi. 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
"I...am...Truth! The voice of the Covenant!"

- The Prophet of Truth

"And so, you must be silenced."

- Thel 'Vadam

After Thel and John entered the Citadel, the Flood formed a tentative alliance with them in order to kill Truth and abort the firing of the Halo Array. Fighting through the Loyalist forces, the unlikely comrades stood before the last Covenant High Prophet. The Arbiter approached Truth, who had been infected by the Flood. The Gravemind spoke through Truth, informing him that he was deluded into thinking he could achieve godhood. Thel claimed 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.

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 Separatist forces from the Ark. The Arbiter took part in the operation to rescue Cortana from High Charity. He used a Flamethrower to cover their escape as High Charity self destructed.

The two then escaped on a D77H-TCI 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 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. Cortana 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 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 Great Journey. Some, such as Avu Med 'Telcam, 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
"I remember how this war started. What your kind did to mine... I can't forgive you... but, you have my thanks. For standing by him to the end. Hard to believe he's dead..."

- Lord Hood

"Were it so easy."

- Thel 'Vadam

In February 2553, 'Vadam met with Admiral Lord Terrence Hood, along with Captain Serin Osman and Dr. Evan Phillips in the State of Vadam on Sangheilios. 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. After being thanked by Hood for "standing by him to the end", 'Vadam responded, "Were it so easy". Knowing the reslience of the Spartan first hand, Thel expressed doubts as to warrior's death. The Arbiter departed for Sanghelios aboard the Shadow of Intent as the ship master, with Rtas 'Vadum, to insure the security of their people.

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.

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.

Combat
"Parasite! Rise up and I shall kill you -- again and again!"

- Thel 'Vadam to the Flood

Thel 'Vadam is approximately seven feet and ten inches, and possesses large three fingered hands. Because of this, Thel struggles to hold guns such as Magnums or Plasma Pistols. In Halo 2, numerous small graphical and gameplay differences exist between the Arbiter and the Master Chief. When playing as the Arbiter, the Chief's flashlight is replaced by an Active Camouflage feature, exclusive to Halo 2; due to the antiquated armor of the Arbiter, the camouflage does not last forever -- it lasts for ten seconds on Easy and Normal difficulties, and five seconds on Heroic and Legendary difficulties. The Arbiter bleeds purple blood instead of red, and his Heads Up Display is sleeker. The Arbiter's HUD is also a purple color, rather than the Spartan blue; in Halo 3 it is teal and is presented in a more curved fashion than Player One's. Player Three and Four's HUDs are also more curved as they too are Elites. In Halo 2, the sound his shield makes when it is depleted is different from that of the Master Chief's. In Halo 3, he still has Active Camouflage, but it is only illustrated in the first cutscene of the game and to elude enemies -- it cannot be used when playing as the Arbiter. He has a flashlight on his left shoulder in Halo 3, which can be used by players in Co-op.

The Arbiter is very experienced at combat, as shown by his relatively extensive knowledge of every weapon and vehicle -- the Arbiter expressed a desire to understand human weapons even before his alliance with the UNSC. His most commonly used weapons are the Plasma Rifle, Energy Sword, and the Carbine; however, if the Arbiter character is being used in Co-Op Campaign, he can wield any weapon the player chooses -- the Plasma Rifle, Energy Sword, and Carbine would only be level-start weapons.

In Halo 3, the Arbiter is a very useful ally against the Flood when he has his Energy Sword out, but when fighting Covenant forces on his own on Heroic and Legendary, the NPC Arbiter tends to be knocked out frequently, for long periods of time, especially on Legendary. This is mostly due to his tendency to lead suicidal charges with his Energy Sword, despite the enemy's great distance from him, another example of the Sangheillian code of honor getting in the way. However, he is useful on Normal and Easy. Also note that when given a Missile Pod (using the support weapon glitch, or putting it by his unconscious body) the missiles will lock onto enemy NPCs.

Reception
Reception to Thel 'Vadam's inclusion within the Halo series has been mixed both critically and by fans. The image that Bungie produced for the marketing of Halo 2 prior to its release was one featuring John-117 defending fighting the Covenant on Earth. Once the game was released, this was shown to be the case until the level, The Arbiter, when the player abruptly took the role of the Arbiter of the Covenant. While many review publications praised the added dimension towards the Covenant and increased the complexity of the plot, this decision still had its fair share of critics. Many fans of the series and critics were displeased with the abrupt switch in character or thought its execution was poor. Some believed it ultimately distracted the player from Earth's fate.

Responding to some of the negative backlash, Bungie decided not to include levels designed solely from Thel 'Vadam's perspective into Halo 3, though he was retained as a playable character for co-op campaign. However, this decision also received a mixed reception from fans and critics. Some believed that the exclusion of Thel 'Vadam as a main playable character greatly diminished the Sangheili's role in the plot, and as a result, erased what might have been an incredibly interesting addition to Halo 3. While others believed Thel 'Vadam was much more likable as a secondary character.

Bungie developers have commented on some of the negative backlash towards the use of Thel 'Vadam in the Halo series. Jaime Griesemer stated "I'd much rather experiment and do something surprising, and not have everybody appreciate it, than just turn the crank and do another alien war movie with a space marine,". Community lead Brian Jarrard attributed some of the fan backlash to a discord between the game's marketing and the actual gameplay. "I think, even more so than playing as the Arbiter, the thing that people were disappointed with and angry about is that they were promised this experience, through the marketing, of being really backs against the wall, Earth's under siege, we're going to do all we can to save our home planet... In reality, the game only had two missions that actually did that." Referring to Halo 2's cliffhanger ending, Griesemer said, "I think if we'd been able to finish that last couple of missions and get you properly back on Earth, a lot of the reaction would have been placated."

Thel 'Vadam is included in MSNBC's list of the "Top 5 Best Aliens in Video Games."

Identity
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.

"During the geocultural review of Halo 2 ’s content, the original name for the Arbiter character -- Dervish -- was identified as a potential problem. Out of context, the name ‘Dervish’ wasn’t too sensitive as it’s a title from the Sufi sect of Islam. However, within the game’s context this Islamic-related name of ‘Dervish’ set up a potentially problematic allegory related to Halo 2 ’s plot -- the U.S.-like forces (Master Chief/Sarge) versus Islam (the religious Covenant, which already had a “Prophet of Truth” which is one synonym for Mohammed). Mind you, this was not too long after 9/11 so the sensitivity to such issues remained high. In the end, the character name was changed to ‘Arbiter’ -- which in my opinion worked much better for the character’s role in the narrative."

- Tom Edwards, geographer and geocultural consultant.

Prior to the release of Halo: The Cole Protocol, there was much speculation on the exact identity of the Arbiter before he was forced to accept the rank. Some believed him to be Orna 'Fulsamee, the shipmaster of a Covenant Destroyer in the Fleet of Particular Justice, pointing out his apparent considerable authority over the fleet and the fact that a Prophet traveled aboard his ship. Others insisted that the Special Operations Commando that the Master Chief wounded in hand-to-hand combat aboard the Ascendant Justice was the Arbiter, given that the Ascendant Justice was described as a Flagship. The fact that the Supreme Commander was shown in the Halo Graphic Novel to use the Flagship Seeker of Truth, and not the Ascendant Justice, did not do anything to quell the speculation until the release of Tobias Buckell's novel four years after the revelation of the character, which even then made only a single reference at the very end of the story to the fact that the Elite the plot had been following for the entire book had been promoted to Supreme Commander of the Fleet of Particular Justice.

It wasn't until later videos on Halo Waypoint that the Arbiter was explicitly identified as Thel 'Vadam. Glasslands marks the first time he's referred to as the Arbiter in a book.

Trivia

 * Thel 'Vadam is voiced by the voice actor Keith David.
 * The Arbiter in Halo 2 is considered, during gameplay, the highest ranking Elite in the area. This means that if the player is killed, lower ranked Grunts in the area will become scared and some might say "Leader dead! Run away!" among others, alongside the dialogue they already use when the Arbiter dies ("Arbiter? Dead?!").
 * When the Arbiter activates his Active Camouflage in Halo 2, his eyes will remain visible. This is only visible on Co-Op.
 * In Halo 2, one can see an Elite skull on 'Vadam's right shoulder, similar to the skull on the Legendary shield; it is unclear if the same symbol is on the armor in Halo 3.
 * Thel 'Vadam is the only known Elite witnessed to be branded with the Mark of Shame. However, the Sangheili in Halo 3's campaign also have the Mark of Shame etched onto their armor as a symbol of their allegiance to their Arbiter.
 * Technically, since his trial, he has no name since all honor that he once had has been removed. This is due to the Sangheilian honorific beliefs, with one such belief being that only those with honor should deserve something as prestigious as a name. Thus, his name and honor were stripped by the Prophets before the Elites left the Covenant, explaining why he was only ever referred to as "the Arbiter" throughout Halo 2. With the outbreak of the Great Schism, Thel regained his name (otherwise he could not have removed the honorary -ee suffix to become simply Thel 'Vadam); the continuing use of the word "Arbiter" is likely out of habit and/or respect.
 * The in-game AI for Thel 'Vadam in Halo 3 is described as being very inept in combat, and many reviews have deemed him a useless ally, because many times in game he will stare at a wall or shoot allies. In Crow's Nest on the part where the player must rescue Marines in the barracks, Thel is known to stare at walls and not fire his weapon. Sometimes he will not follow the player on parts where he is scripted to do so, and tends to die often, particularly on higher difficulties.
 * It is possible to clone the Arbiter in Halo 3 on the level The Covenant. On the part after one exits the second tower, the Arbiter will head to a Phantom for extraction. If the player prevents him from getting to the Phantom by blocking his path, when he gets inside the Phantom, destroy it quickly with the Scorpion and wait a few seconds. After a few seconds of waiting, there are usually two Arbiters. This is not an easy task, and sometimes it does not work. One must work very fast. The clone Arbiter can be useful, as he acts as the original Arbiter would.
 * If one attempts to kill 'Vadam in Halo 3 during Campaign Solo, he will fall unconscious, but he will get up again and pick up any weapon near him. If the player kills 'Vadam for his weapons, his Energy Sword will have a low battery (though occasionally it will be full or near full). Also, if the player kills him twice, he will get up and calls the player a traitor, then kill the player with a single shot with whatever weapon he happens to be holding. If he is left alone for awhile, he will forgive the player and act as a teammate again.
 * 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.
 * Interestingly enough 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.
 * In the story Last Voyage of the Infinite Succor, from the Halo Graphic Novel, 'Vadam is shown in purple ceremonial command armor, and is in command of the Seeker of Truth. Due to this, it is believed by some that the Ascendant Justice was made the flagship of the fleet after the Supreme Commander and most of his forces evacuated the Threshold system. Thus, Tartarus and the Prophet of Truth may have referred to him as "the incompetent who lost Ascendant Justice" due to the events that transpired that resulted to the loss of the ship, not because he was directly responsible for losing it in combat against the Master Chief.
 * In Halo 2, the Arbiter has no mandible guards, but he does in Halo 3. Notably, the armor of the previous Arbiter, Ripa 'Moramee, did possess mandible guards.
 * 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, "arbitro", means "referee".
 * One should take notice of the Arbiter on higher difficulties. When he is killed, he might somehow lose his long ranged weapon, making him only useful in close combat. When this happens, make sure one gives him a long ranged weapon when he is knocked out.
 * If one kills the Arbiter, takes his weapon, and gives him a weapon with no ammo, he will not pick up any weapons, and will be weaponless. This can also be achieved by giving the Arbiter a support weapon and getting him to ride in a vehicle.

List of appearances

 * Halo: First Strike
 * Halo 2
 * Halo Graphic Novel
 * The Last Voyage of the Infinite Succor
 * Halo 3
 * Halo: The Cole Protocol
 * Halo: Evolutions - Essential Tales of the Halo Universe
 * The Return
 * Wages of Sin
 * From the Office of Dr. William Arthur Iqbal
 * Halo Legends
 * Origins
 * Halo: Glasslands