Halo characters explained: Master Chief, Cortana, Arbiter, more

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Halo has some of the best characters in all of science-fiction. From brave heroes to sympathetic antagonists, here’s a breakdown of the Halo characters ahead of Halo Infinite.

The Halo series is comprised of some very layered characters, many with complicated and morally grey motivations that go beyond typical good and evil. Halo characters often come with intriguing backstories and each one offers insight into certain themes.

Through its characters, Halo has explored concepts such as loyalty, faith, companionship, race, and hatred, with each new antagonist bringing a new layer to the game’s story. Most Halo characters belong to a certain faction or species, so we’ve broken them down based on this.

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We’re only covering characters that are still alive in the Halo universe, or who could feasibly return in the upcoming Halo Infinite. This will release on December 8, 2021, on Xbox Series X|S, Xbox One, PC, and Xbox Game Pass.


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Halo Infinite is the next chapter in the franchise.

United Nations Space Command (Human) characters

In the 26 century, humanity has spread across the stars, colonizing planets, and peacefully coexisting with extra-terrestrials they encounter. This is until they come across the Covenant, a militaristic alliance of several alien species that view humanity as an afront to their religion.

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After 20 years of war, humans create a race of super-soldiers called Spartans who are able to push back against the Covenant. However, after the Fall of Reach, an important human settlement, the Covenant kills most of the Spartans and turns its attention to Earth. This is when Halo 1 begins.

Since then, humans have made peace with the Covenant and defeated their mutual enemy the Flood. However, as conflict has continued across the galaxy in other forms, the human-built AI Cortana has developed her own frightening strategy to ensure peace, setting the scene for Halo Infinite.

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Master Chief

Master Chief ready for a mission343 Industries
Master Chief remains one of gaming’s most iconic characters.

Petty officer John 117 or Master Chief is the main protagonist and playable character throughout the Halo series. Chief is one of the last remaining Spartans after the harrowing finale of Halo Reach, making him an endangered species and a valuable weapon. He is responsible for defeating the Covenant zealots and the Flood, ending the war from the original Halo trilogy.

However, since then, new threats have emerged in the form of Promethean Knights, resurrected Forerunners, and their superweapons. In Halo Infinite, Chief’s story is set to be more personal, as his mission is to stop Cortana, his AI ally and closest friend throughout the earlier games.

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Cortana has taken control of Forerunner weapons called Guardians. She has also activated a new Halo array to force the galaxy into submission under her rules. Master Chief needs to convince Cortana to stand down before she commits an act of genocide, or before she’s destroyed by either Chief or some other force.

Spartan Locke

Lock and Chief fight343 Industries
Locke tries to arrest Master Chief.

A playable character in Halo 5: Guardians, Locke is part of a new generation of Spartans sent to apprehend Master Chief after he disobeys orders. This leads to several skirmishes between the two with Locke believing Master Chief is a traitor.

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However, after spending some time helping the Arbiter battle Covenant zealots and Promethean Knights, Locke begins to understand Chief’s motivations more. Spartan Locke is likely to return in Halo Infinite as a supporting character and in multiplayer.

Covenant characters

The Covenant starts out as the main antagonists of the Halo series. Led by the three Prophets, Regret, Mercy, and Truth, the Covenant wages war against Earth to try and eradicate all human life. This is because their teachings warn of humanity’s destructive potential and that the Covenant’s Gods, the Forerunners, also once needed to destroy them, at the cost of their own lives.

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They essentially see humans as demons that will bring about the destruction of all sentient life as they once did before. However, during the first Halo game, it’s revealed that the Covenant has misunderstood their teachings. The Forerunners are actually warning the Covenant about the Flood, and humanity was simply one race that (regrettably) needed to be eradicated to stop the Flood from spreading.

In Halo 2, civil war breaks out among the Covenant when the Prophets refuse to budge from their fanatical views, despite evidence suggesting they were wrong. While the Prophets continue to try and destroy humanity, the rest of the Covenant forces, led by the Arbiter, make peace with humanity and help them combat the Flood and the Prophets.

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By the end of Halo 3, the Prophets and the Flood have been defeated and there is peace between humanity and the Covenant. However, the civil war continues as some Covenant forces remain committed to the lie that was their religion.

The Arbiter

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The Arbiter and Master Chief battle back-to-back.

The Arbiter is the leader of the Sanghelios race who are members of the Covenant. After failing to defeat humanity in the original Halo, he is punished by the Prophets and sent on a mission to redeem himself. Although he is later betrayed and marked for death by the Prophets.

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After learning the truth about the Flood and the false Covenant teachings, the Arbiter rebels and helps Master Chief battle both threats. He eventually forges an alliance between the Covenant and humanity and even aids Master Chief in later battles. This includes Covenant still loyal to the old religion who have rejected peace with humans.

The Arbiter is able to defeat these rebels in Halo 5, but the Covenant are then dragged into a new fight against the Prometheans and Cortana. This risks destabilizing the peace between humanity and the Covenant when Master Chief goes rogue.

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Flood characters

The Flood are the main antagonists of the Halo universe and from which every conflict stems. They essentially turn living matter into zombies and assimilate them into their hivemind. The Halo array superweapons were built by the Forerunners to destroy the Flood and to stop their threat from spreading further.

While the Flood was defeated in Halo 3, their return is something every character in Halo fears most. Combatting the Flood can make even the bitterest of enemies join forces in an effort to stop them.

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Gravemind underground343 Industries
Gravemind in his true terrifying form.

Intelligent, cunning, and utterly ruthless, Gravemind is the sentient representative of the Flood. Often appearing reasonable and measured, Gravemind explains that the Flood is simply doing what comes naturally to them and that they have a right to exist – and exist their way.

Gravemind often appears as a collection of tentacles or a plant-like creature. However, it has a deep understanding of space travel and technology, possessing the ability to take over whole ships and pilot them to pursue its enemies through slip space.

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All Gravemind wants is to spread the Flood across the universe. It’s even willing to ally with Master Chief and The Arbiter to stop the Covenant Prophets from activating the Halo arrays, which would destroy its hosts. However, as soon as the Halo threat is over, Gravemind betrays and tries to assimilate any allies it has.

Gravemind is seemingly killed at the end of Halo 3, but it’s always unwise to underestimate the ancient intelligence that controls the Flood.

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Forerunner characters

The Forerunners are an ancient civilization that occupied the galaxy before humans and the Covenant. They were driven to near extinction by the Flood as planet after planet was infected by Gravemind. They were so desperate to eradicate the threat, that they built Halo arrays, superweapons capable of stripping all sentient life from the galaxy.

It’s believed that these Halos led to the near-total destruction of the Forerunners and the Flood. The Forerunners also used a Halo array against humanity, sending us back to the stone age, but free from Flood infection and able to start again.

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The Covenant worshipped the Forerunners as Gods and saw the destruction of humanity as a holy mission that they had inherited. This is once it is discovered that humans had become a space-faring race once again.

However, most of the Covenant have turned their back on this idea and this religion. This is after discovering that the Forerunners were just as flawed as anyone else, and that their true enemy was the Flood, not humanity.

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The Didact

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The Didact explains why humans cannot be trusted.

A great Forerunner leader and warrior, the Didact is the main antagonist of Halo 4. He awakens from an eons-long hyper-sleep to learn that the Flood has returned and that humans now hold the Mantle of Responsibility. This means they are tasked with keeping the galaxy safe from the Flood.

Disgusted by this, the Didact wages war against both humanity and the Covenant until he’s defeated by Master Chief. While his body is destroyed, his consciousness is imprisoned somewhere known as the Domain.

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As the Didact is now essentially an AI, his return in Halo Infinite is highly plausible. This is because Cortana is using an army of AIs to do her bidding and the Didact could make a powerful weapon. It was, after all, his technology that allowed Cortana to evolve into her new form.

The Librarian

The Librarian is the Didact’s wife who also still exists in a non-corporeal form. While she still loves her husband, she fears he is beyond redemption. Before the destruction of the Forerunners, the Librarian and Didact fundamentally disagreed on how to deal with the Flood.

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While the Didact wanted to use Halo arrays to destroy civilizations like humanity, the Librarian declared herself to be their protector to try and stop him. While she failed in her initial quest, she managed to help Master Chief fulfill this role in Halo 4.

Promethean Knights

The warden eternal in Halo 5343 Industries
The Warden Eternal is the leader of the Promethean Knights.

Not much is known about the Prometheans and there haven’t been many individual characters within their ranks either. The Promethean Knights may have been biological weapons created by the Forerunners to battle the Flood. This explains why they were quick to ally with the Didact in Halo 4.

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In Halo 5 the Prometheans are still active but have splintered into multiple groups. Some have sided with Cortana while others are still loyal to the Didact and have waged war against the Covenant. One Promethean Knight known as Warden Eternal served as Cortana’s enforcer in Halo 5, but was ultimately destroyed by Master Chief.

AI characters

Artificial intelligence has become increasingly pivotal in the Halo series. Several Halo characters are AIs or started out as AIs. While there are several active AIs by the end of Halo 5, these are the most important ones in the series:

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Cortana in Halo343 Industries
Cortana is trying to save the galaxy, but some believe she’s trying to rule it.

Cortana is Master Chiefs’ loyal and faithful AI companion and has helped him save humanity and bring peace to the galaxy since Halo 1. Cortana was instrumental in defeating the Flood and the Covenant zealots but was seemingly destroyed in the battle against the Didact in Halo 4.

However, in Halo 5 it’s revealed Cortana has used Forerunner technology to restore herself and expand her consciousness to become something more than an AI. Realizing that humans, Covenant, and other races will always find reasons to fight, Cortana takes control of various Forerunner superweapons to force peace through the threat of annihilation.

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Of course, intelligent life across the galaxy doesn’t take kindly to Cortana’s threats, and the quest to find and destroy her begins. Master Chief aims to find and stop Cortana peacefully before either she or any of his allies are harmed.

343 Guilty Spark

Guilty spark warns Master Chief343 Industries
Guilty Spark can’t let go of his ‘purpose’.

Guilty Spark is an AI built by the Forerunners to watch over the first Halo array from Halo 1. When this is destroyed, he joins Master Chief as he now has no purpose other than the eradication of the Flood.

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While serving as a helpful ally in Halo 2, Chief is forced to destroy him in Halo 3 when he becomes obsessed with the second Halo array and tries to activate it, despite the risk this poses to humanity. He also kills Master Chief’s commanding officer in this exchange, forcing Chief’s hand.

However, other Halo media reveals that Guilty Spark still exists and is monitoring the Didact. As Halo Infinite is focused on the threat of AI growing too powerful, could we see Guilty Spark return?

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Want more details on Master Chief’s next outing? Here’s everything we know about Halo Infinite in one place.

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