Warning! Spoilers ahead for Halo episode 2.
Soren-066, the only SPARTAN-II dropout and John-117's friend, Master Chief takes Kwan Ha to The Rubble in an attempt to evade the UNSC forces after he went rogue, refusing to kill Kwan while also keeping the Forerunner artifact in his possession. The Rubble is also a location that's been referenced in the tie-books and comics, having its own history in the games' timeline that the new live-action series clearly takes inspiration from.
In Halo episode 1, Master Chief and his SPARTAN unit Silver Team were tasked with intercepting a Covenant attack on the colony world of Madrigal. This is where John-117 came into with Kwan as well as the Forerunner artifact the Covenant warriors had been searching for. Touching the artifact, Master Chief ended up activating the device which gave him visions—potentially his own fragmented memories that Doctor Halsey and the SPARTAN program had removed during his training. This is what motivates Master Chief to defy orders, sparing Kwan's life and heading for The Rubble as a means to escape the UNSC, giving him time to learn more about his connection to the artifact (revealed to be a Forerunner keystone).
Making its first appearance in Halo: The Cole Protocol by Tobias S. Buckell, The Rubble is one of the few hidden areas in the galaxy that wasn't under the control of the UNSC or the Covenant. That being said, the version seen in the new Halo series doesn't seem to be as complex as the one from the novels, keeping its focus on those seeking to escape the notice of the UNSC. Here's the history of The Rubble and its location in the greater Halo galaxy.
Where The Rubble Is Located In Halo's Galaxy
The Rubble is a collection of asteroids in the 23 Librae system. The colony world of Madrigal (featured in Halo episode 1) and the gas giant Hesiod reside within 23 Librae as well. Created by insurrectionists and rebels with no love for the UNSC, the Rubble promised freedom among its many asteroids connected by a multitude of docking tubes, allowing its residents to travel back and forth to the markets and settlements that resided within the giant hollowed-out rocks floating through space. It also became a refuge for survivors of Madrigal when the Covenant glassed the planet in the novels (something which could happen down the line as the Halo series continues).
While not a part of the live-action series version, The Rubble was also home to a faction of alien Kig-Yar (also known as Jackals). Appearing to have no love for the Covenant, the humans of the Rubble and the Kig-Yar had established an uneasy alliance based on trade. However, this doesn't appear to be the case with the version of The Rubble featured in the Halo series' Silver Timeline.
What Happens To The Rubble In Halo
In the continuity of the games and tie-in novels, The Rubble ultimately fell to ruin and was destroyed after it was eventually discovered by both the Covenant and the UNSC forces. Furthermore, it was revealed that the Kig-Yar faction living on The Rubble were secretly under orders from the Covenant's Prophet of Truth to try and determine the location of Earth. Furthermore, they were also secretly building an army of Grunts on Hesiod's nearby moon with the intent to eventually betray the humans living inside the collection of asteroids.
While the Kig-Yar's influence doesn't appear to be a factor in the Halo series, The Rubble eventually becoming caught in the crossfire of Halo's Human-Covenant War could certainly come into play as the series continues. Master Chief did inadvertently activate the Forerunner object while inside the asteroid colony, potentially acting as a beacon for the Covenant to follow. Either way, this probably won't be the last viewers will see of The Rubble in Paramount's Halo, especially after Master Chief left Kwan with Soren before heading back to the UNSC.
Halo releases new episodes Thursdays on Paramount+.