Onyx’s Importance & Secret Forerunner Connection In Halo Season 2 Explained
8 mins read

Onyx’s Importance & Secret Forerunner Connection In Halo Season 2 Explained

Spoilers are ahead for Halo season 2, episode 5, “Aleria.”




  • Halo
    season 2 has introduced Onyx, but has yet to hint at its Forerunner connection.
  • To start,
    explores the importance of Onyx as a training base for James Ackerson’s Spartan-IIIs.
  • The concept of shield worlds (and the aftermath of Installation-04) plays a significant role in Onyx’s story.

The glimpse viewers get of Onyx at the end of Halo season 2, episode 5, “Aleria,” might tease the location’s importance, but it does little to reveal the planet’s secret Forerunner connection. The majority of “Aleria” takes place on the episode’s titular planet, following Master Chief (Pablo Schreiber), Dr. Catherine Halsey (Natascha McElhone), Riz-028 (Natasha Culzac), Kwan Ha (Yerin Ha), and the other Reach survivors who landed on the outer colony. Fittingly, after Halo reveals that the UNSC abducted Kessler (Tylan Bailey), the son of Laera (Fiona O’Shaughnessy) and ex-Spartan Soren (Bokeem Woodbine), the Paramount+ series cuts Onyx.

In its final moments, episode 5 confirms where Kai was during the Fall of Reach: Kate Kennedy’s Silver Team Spartan followed Halsey’s replacement, James Ackerson (Joseph Morgan), when he fled Reach. Even before Silver Team’s ill-fated expedition to the Visegrád comms relay, Ackerson was subtly manipulating Kai-125 in order to break the trust between her and John-117 (Schreiber). Seemingly Ackerson’s right-hand Spartan, Kai looks out over a battalion of newly minted Spartan-IIIs lined up outside the UNSC base on Onyx. However, Onyx’s importance doesn’t just hinge on Ackerson’s fresh batch of soldiers.

Onyx Is Where Spartan-IIIs Are Trained In The Halo Series

Onyx, also known as XF-063 by the UNSC, was dubbed a “rare jewel of a find” thanks in part to its human-habitable surface. During the Human-Covenant War in Halo‘s core canon, Onyx is the headquarters of Ackerson’s Spartan-III program. When the UNSC Engineering Corps discovered Onyx prior to the start of the Human-Covenant War, colonization of the planet didn’t happen on the same scale as it did in other comparable locations. In fact, the discovery of alien technology led ONI, the Office of Naval Intelligence, to take control of the planet.


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After removing Onyx from UNSC navigational databases, ONI kept the planet’s location a closely-guarded secret. Just before the start of the Human-Covenant War, Onyx boasted a single ONI garrison overseen by A.I. constructs. During the war, Vice Admiral Parangosky (played in the show by Shabana Azmi) authorized Ackerson’s request to construct a Spartan-III training base on Onyx. Dubbed Camp Currahee, the base was the secret home to Ackerson’s brainchild — the successor and supplement to Halsey’s Spartan-II Program. In the show, Onyx seems to serve the same purpose with regard to housing Ackerson’s program.

Halo’s Onyx Is Actually A Forerunner Shield World

Onyx planet from Halo series

The UNSC and ONI didn’t just discover traces of alien technology on Onyx. In fact, Onyx isn’t really a planet at all. Instead, it’s a planet-sized Forerunner shield world. In order to combat the Flood — a parasitic being intent on consuming all sentient life in the galaxy — the Forerunners devised two strategic plans. First, they developed the Halo array — a superweapon capable of sterilizing the whole galaxy. The shield worlds, however, are more defensive-minded in that they serve as refuges and military fortresses. Moreover, shield worlds protect their inhabitants from the Halos’ life-ending pulses.

It would be wise to introduce a shield world prior to the discovery of Installation-04.

Also known as Shield World 006 or Sarcophagus, Onyx is one of many shield worlds. Essentially, the artificial planet (what the UNSC dubbed Onyx) serves as a kind of shell that guards the entrance to the shield world proper. That inner component, known as a Dyson sphere in Halo‘s core canon, is basically a massive habitat that’s cradled safely in a slipspace bubble. While the Halo show changes Forerunner-human lore in many instances, it would be wise to introduce a shield world prior to the discovery of Installation-04 — the Sacred Ring from the first-ever Halo game.

Onyx Is Important In The Wake Of Installation-04’s Destruction

In Halo: Combat Evolved, Master Chief destroys Installation-04 after Cortana reveals the Sacred Rings’ true purpose: to destroy the galaxy’s sentient life. However, John-117’s aborted attempt at the firing of Installtion-04 activates the Forerunners’ Onyx Sentinels, leading to the Onyx Conflict. The battle between the artificial planet’s Forerunner Sentinels and the UNSC’s Spartan-III soldiers reveals the location’s true nature once and for all. Amid the chaos, both the UNSC and Covenant dispatch teams to retrieve Forerunner tech from Onyx before it’s destroyed. This leads to an all-out, triangulated battle between the three forces.

season 2’s finale will air on March 21, 2024.

Eventually, the Sentinels decimate Onyx’s surface, destroying the remaining Covenant species and lingering human survivors. Later, concentric rings of debris orbit the place Onyx had once been, indicating that the slipspace bubble and Forerunner shield world that were hidden by Onyx’s artificial surface survived the skirmish. ONI takes an interest in the late location of its Spartan-III training base and transforms the shield world into a research facility, which is later dubbed the Onyx United Research Project as an ode to the former artificial planet. That said, Onyx plays a huge role in introducing the concept of shield worlds.


Halo’s Arbiter Revealed In Season 2, Potentially Changing The Story Massively

Halo just confirmed the identity of the show’s Arbiter in season 2, episode 5, “Aleria,” which potentially changes the whole story in a massive way.

Halo Season 2, Episode 6 Is Called “Onyx” For A Reason

Kai (Kate Kennedy) addresses Perez (Cristina Rodlo) and other UNSC soldiers in Halo season 2

All of Halo season 2’s episodes have been named after important locations, from “Visegrád,” a reference to the comms relay, to “Reach” itself. Halo season 2, episode 6 is called “Onyx,” which means the series is placing a little extra emphasis on the iconic franchise location. There’s no denying that Halo‘s “blessed ones” — human beings whose genetics allow them to activate Forerunner technology — have taken the series in a very different direction. While the sophomore outing has tried to meld new and preexisting elements, it’s hard to imagine how the show will handle the shield world.

With a piece of the Halo array, a shield world, and the Flood all potentially in play, Paramount+’s
series will have successfully set up some of the franchise’s most crucial and fan-loved elements.

Nonetheless, it’s great to see Halo season 2 introducing Onyx ahead of the show’s third outing. Based on Kwan Ha’s vision, Halo season 3 is primed to introduce the Flood. Not to mention, Makee (Charlie Murphy) and The Arbiter, a.k.a. Var ‘Gatanai (Viktor Åkerblom), are seemingly headed toward the show’s version of Installation-04. With a piece of the Halo array, a shield world, and the Flood all potentially in play, Paramount+’s Halo series will have successfully set up some of the franchise’s most crucial and fan-loved elements. While Onyx is just one of those aspects, it’s a huge step in the right direction.

Source: Halopedia

  • Halo Season 2 Hero Showing Master Chief carrying a fallen soldier on the battle field


    Release Date:

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    Adventure, Sci-Fi, Action


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    Otto Bathurst, Jonathan Liebesman, Roel Reiné, Dennie Gordon, Debs Paterson, Craig Zisk, Jessica Lowrey

    Kyle Killen

    Kyle Killen, Steven Kane

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