WARNING: The following contains spoilers for The Expanse Season 6, Episode 6, "Babylon's Ashes," available to stream now on Prime Video.
After six seasons, The Expanse has concluded, with the war against the villainous Marco Inaros and his Free Navy serving as the explosive through line of the final season. And with Marco killed along with his remaining loyalists by the end of The Expanse's series finale, there are still plenty of loose plot threads and surviving characters that are practically begging for some sort of continuation or spinoff series. In addition, there are three novels' worth of untouched material by franchise creators James S.A. Corey to draw from and adapt for a potential spinoff.
The Expanse Season 6 primarily adapts material from the novel Babylon's Ashes, even taking the title for its series finale, while the prologue to each episode in Season 6 adapted the novella Strange Dogs and the reemergence of the protomolecule on the colonized world of Laconia, beyond the Ring Gates at the fringe of the solar system. This leaves the novels Persepolis Rising, Tiamat's Wrath and Leviathan Falls; these three novels featured a 28-year time jump between the series and the Free Navy's defeat, making The Expanse ending its main run with Marco's death as a natural pause point in the overarching narrative.
In Season 6's prologues, the head of the Laconia colony is revealed to be Winston Duarte, an officer presumably heading the Martian researchers on the planet. As Season 6 continues, Duarte is revealed to be in contact with Marco and operating outside of the authority of the Martian government opposing the Free Navy, ultimately betraying Marco by refusing him safe passage to Laconia. A spinoff could chronicle Duarte's rise to power on Laconia, eventually pitting him against the main characters, a matter further complicated by Laconia possessing such a large deposit of the protomolecule, the extraterrestrial substance that has played such a major role in earlier seasons and infected any organic matter that came into direct contact with it.
Even beyond Laconia and the protomolecule, there are plenty of interesting directions for its surviving characters to go next. Camina Drummer is now the head of the newly created Transport Union, an independent organization tasked with regulating travel through the Ring Gates to worlds beyond the system. This effectively makes her one of the most powerful people in the system, while a fragile peace between the Belters, Earth and Mars remains ripe for a continued story. Drummer's rise to power coincided with Marco's son Filip going on the run, deserting his father's cause and on a path of redemption as he rejected the violent example that Marco provided him, the perfect path for a reluctant protagonist.
Marco and the Free Navy have been defeated, offering humanity a measure of peace after a war that left Earth and Mars devastated and Belters all over the system starving from Marco's calculated neglect. However, the mystery of the protomolecule is far from over and in the grasp of a character potentially more nefarious than Marco himself as Duarte continues to reveal his true colors. And while there's been no official word of an Expanse spinoff yet, the series finale left plenty of directions and untouched source material for the story to go next if given the opportunity.
Developed for television by Mark Fergus and Hawk Ostby, all six seasons of The Expanse are streaming now on Prime Video.