Cortana
Advanced AI construct created from a clone of Dr. Catherine Halsey's brain, Master Chief's closest companion.
Personality
Abilities
Notable Items
"Don't make a girl a promise... if you know you can't keep it."
Gravemind

Collective consciousness of the parasitic Flood, representing the ultimate threat to all sentient life.
Personality
Abilities
"I am a monument to all your sins."
Master Chief Petty Officer John-117

Legendary Spartan super-soldier and humanity's greatest warrior in the fight against alien threats.
Personality
Abilities
Notable Items
"I need a weapon."
Master Chief Petty Officer John-117

Legendary Spartan super-soldier and humanity's greatest warrior in the fight against alien threats....
Abilities
Prophet of Truth

Manipulative leader of the Covent who seeks to activate the Halo rings for religious purposes.
Personality
Abilities
"I am Truth! The voice of the Covent!"
Sangheili (Elite)

Proud warrior race that served as the military backbone of the Covent before the Great Schism.
Personality
Abilities
"Wort wort wort!"
Thel 'Vadam (The Arbiter)

Former Covent Supreme Commander who becomes an ally to humanity after learning the truth about the Halo rings.
Personality
Abilities
Notable Items
"Were it so easy."
Thel 'Vadam (The Arbiter)

Former Covent Supreme Commander who becomes an ally to humanity after learning the truth about the...
Abilities
Unggoy (Grunt)

Small, methane-breathing aliens serving as cannon fodder in the Covent military hierarchy.
Personality
Abilities
"Run away! Run away!"
UNSC Marine

Brave human soldiers fighting on the front lines against overwhelming alien forces.
Personality
Abilities
"Oorah! Let's get some!"
Ur-Didact

Ancient Forerunner military commander driven mad by imprisonment and torture, seeking revenge on humanity.
Personality
Abilities
"So fades the great harvest of my betrayal."