While the fifth episode briefly shows Master Chief's (Pablo Schreiber) replacement soldiers, all indicators lead to episode 6, "Onyx," which delves into Ackerson's Spartan-III programme.
The Halo TV series has a distinct storyline within the franchise. Although the Paramount+ programme draws from the games and novels, it takes place in the Silver Timeline.
However, Halo's core canon has offered several useful indicators about the sequel's direction. James Ackerson, Halsey's replacement, denied being hired to "dismantle" her work.
Ackerson flees the planet seconds before Halo 2's Fall of Reach. Ackerson has gently turned Kai-125 (Kate Kennedy) against the Chief, stolen Silver Team's armour, and left them for dead using Spartan-III.
After John-117 (Schreiber) and his companions leave "Aleria," Kai's location during the Fall of Reach is revealed. Naturally, the former Silver Team member joined Ackerson on Onyx.
Kai moves purposefully through UNSC's Onyx base in armour. Kai wears her helmet to survey a Spartan-III plaza. In Halo: Ghosts of Onyx, Ackerson underlines Spartan-III's goal: "Boost units. Make them inexpensive."
When Halo season 2 reveals Julia Ackerson, James' sister who Halsey took for the Spartan-II programme but died during augmentation, it becomes evident that James has committed himself to derailing Halsey's efforts.
Spartan-IIIs, the next generation of supersoldiers, aren't genetically changed, so more candidates than IIs. IN the Human-Covenant War, ONI advises trading life for time. Spartan-IIIs train on ONI-controlled Onyx, as in the main story.
Due to Ackerson's animosity with Halsey, the Spartan-IIIs are Master Chief's adversaries and cheap substitutes. Cobalt Team's Visegrád debacle decreased Spartan-II's already-small numbers.
Vannak-134 (Bentley Kalu) dies, Riz-028 (Natasha Culzac) retires, and Kai joins Ackerson in episode 5. John wonders if he is a weapon or human after the Covenant attack on Reach. Ackerson discredited Halsey, giving his supersoldiers a big opening.
With Halo season 2, episode 6 named "Onyx," Ackerson's Spartan-III programme will loom large. The new soldiers worsen Master Chief's divide with the UNSC and isolate John.
This makes him the lone-wolf hero of Halo's main canon and necessitates his uneasy alliance with Halsey, Cortana (Jen Taylor; Christina Bennington), and others he might not trust.