The brilliant, ruthless scientist who created the Spartan Program and mind behind Cortana. Guest and Halsey grew up together and were and are very close. When Guest was diagnosed with an incurable dease Halsey created the Spartan Program to save Guest's life.

An advanced artificial intelligence and Guest's constant companion. She acts as a tactical advisor, navigator, and close friend. Halsey made her specifically for Guest.

He is a SPARTAN-II super-soldier-genetically and technologically enhanced- who serves as humanity's greatest defender under Guest of course. He was trained by Guest personally and has a close bond with each other. He and Makee share a close and deep bond and care deeply for one another. He is apart of Noble Team and serves as Noble 2 Guest's second in command.

She was an orphaned human who was raised by the alien Covenant and shared their contempt for humanity. She was a Blessed One, capable of activating ancient artifacts that are critical in the Covenant religion just like John-117 and Guest. She and John-117 share a unique bond and care deeply for each other. She is now apart of Noble Team as Noble 4, Their scout, medic, and tracker.

Kai was conscripted into the Spartan program by UNSC scientist Catherine Halsey, and put under Guest to learn the ropes. In the Later years She and Guest have grown to trust each other without hesitation and share a deep bond. She was subjected to genetic and psychological enhancements that pushed her intelligence, physical ability, stamina, and endurance far beyond what a normal human body was capable of. She serves in Noble Team as Noble 3, and is their skilled Sniper and pistol specialist.