Released in 2021, Leviathan Falls is the last of nine novels in The Expanse series.
Leviathan Falls contains examples of:
- Ambiguous Ending: A lot of the ending is up to the reader to interpret. Alex's final chapter ends with alarms going off on the Rocinante and him unsure whether the ship will last long enough to reunite him with his family in the Nieuwestad system. Thirty colonies are able to discover a safer form of faster-than-light travel and form an alliance, but it's unclear if this is all that remains of humanity or just one nation of many. Earth appears to be the only inhabited planet in the Sol system and Amos mentions that Earth has had "a rough millenium", but what actually happened is unknown.
- Assimilation Plot: Duarte decides to turn all of humanity into a hive mind controlled by him so he can become capable of operating the weapons the ring builders created to keep their enemies out of the universe.
Word of God states that this was actually part of the Ringbuilder's plan to bring themselves back by hijacking more resilient lifeforms, with Duarte being their first victim. - Big Dumb Object: The BFE, a planet-sized diamond created by the Gate Builders. Cara, and later Amos, can interact with it given the right equipment, and it tells them the history of the race that built it.
- Bittersweet Ending: Duarte is dead, and his Assimilation Plot is foiled, but Holden is forced to destroy the ring network to stop the dark gods, and dies in the process. Everyone in the slow zone is able to evacuate, but any colonies that aren't self sufficient will die of starvation. Alex leaves to be with his son's family in the Nieuwestad system, but the aging Rocinante starts having reactor trouble as he transits, and it's unclear if he reaches his destination. Naomi, Amos, Elvi, and Teresa return to Earth aboard the Falcon and watch the rings disintegrate, with Naomi thinking that one day, humanity will return to the stars.
- Deadly Upgrade: Holden deliberately infects himself with the protomolecule so that he can talk to Miller and convince him to give them a way into the Ring Station.
- Defiant to the End: After being betrayed by Colonel Tanaka, the crew of the Gathering Storm refuses another offer of surrender, choosing to destroy the Sparrowhawk and go down fighting a hopeless fight against the Derecho.
- Disney Death:
- Amos once again gets shot and survives, this time because his transformation has made him immortal.
- Holden shoots Tanaka in the head, but he misses her vitals and a medic is able to treat her wounds.
- Kit and his family get dutchmanned, only for Duarte to intervene and bring them all back.
- Distant Finale: The epilogue takes place a thousand years after the events of the previous chapter, where a linguist from the Thirty Colonies meets Amos on an expedition to Earth.
- End of an Era: The ring station and the gates are shut down and destroyed, removing the threat posed by the aliens, but ending humanity's expansion and dooming potentially hundreds of worlds.
- Extradimensional Power Source: The ring station is revealed to draw power from what is described as 'an older, more primitive universe'. Unfortunately, that universe is full of extremely hostile...things with Reality Warper powers that don't take kindly to its existence.
- It's also revealed that the Magnetar-class battleship's Wave-Motion Gun runs on a similar principle, which explains the event in Sol system in Persepolis Rising.
- First-Name Basis: A more meta example than most. After eight books of the narration calling James Holden by his last name, in this book he is almost always referred to as "Jim", highlighting his vulnerability after years of being a Laconian prisoner.
- Hearing Voices: As Duarte's plan proceeds, everyone starts hearing other people's internal monologue as their consciousnesses are merged.
- Heroic Sacrifice: Holden injects himself with the protomolecule so he can get Miller's help to access the alien station, knowing full well that he has condemned himself to a slow and painful death. What ultimately kills Holden is a second sacrifice, where he shuts down the ring space while he is the only person inside it to save humanity.
- Hive Mind: The Precursors are confirmed to be one. Duarte tries to turn humanity into one to destroy the Dark Gods, and very nearly succeeds.
- Humans Are Cthulhu: Discussed. The San Esteban system is completely killed off by one of the dark gods' experiments that interfered with the functions of neurons. Elvi and Fayez theorize that the only reason they didn't do this to every human world is that humans are as incomprehensible to them as they are to humans. Unlike the builders who came before them, killing the San Esteban system didn't stop humans from continuing to use the gate, which from the perspective of the dark gods means what they tried didn't change anything.
- Humans Are Superior: Duarte, and later Miller say that humans would make a better Hive Mind than the gate builders ever did, due to having robust physical bodies. How true this is is left unclear.
- Last Episode, New Character: The POV character for the epilogue is Marrel, a linguist from thousand years after the previous chapter.
- Last Stand: At the end of the book, the last non-altered humans make a stand at the ring station, trying to hold off the hive mind's fleet long enough to stop Duarte.
- Lovecraft Lite: The dark gods are incomprehensible, immensely powerful, and virtually unstoppable, but all they want is the destruction of the ring station. Once Holden destroys it, they're content to leave the universe in peace.
- Mind Rape: Duarte forcibly merging the consciousness of humanity is compared to an unstoppable, unavoidable, endless sexual assault.
- Near-Villain Victory: Duarte successfully merges the consciousness of everyone outside the slow zone, and then sends hundreds of ships, including the virtually-indestructible Voice of the Whirlwind, into the slow zone to kill off the last unaltered humans.
- No-Holds-Barred Beatdown: Colonel Tanaka kills Duarte in the most brutal fistfight in the series.
- No Ontological Inertia: Duarte's Hive Mind falls apart as soon as he's killed, and his victims suffer nothing more than confusion and lost time.
- Sadistic Choice: As long as the ring gates exist, the dark gods will keep trying to find a way to destroy humanity. Either use the ring station to transform humanity into a Hive Mind that can fight back, or shut down the rings for good, cutting every system off from each other and dooming any colonies that aren't self sufficient. Duarte attempts the former, while Holden chooses the latter.
- Sanity Slippage: As Duarte's Assimilation Plot progresses, every human outside the slow zone begins to share memories and consciousness with each other. Most characters don't take this well at all.
- Shout-Out:
- To Ursula K. Le Guin: there's a ship called Sparrowhawk and Fayez compares Elvi's experiments on Cara to The Ones Who Walk Away from Omelas.
- The last thing Tanaka does before dying is to make finger guns at Holden and yell "Bang, motherfucker."
- The Stinger: A thousand years into the future, a group of humans from the Thirty Worlds reach Earth with an FTL drive. They are greeted by Amos Burton, who offers them some beer.
- Team Pet: Muskrat, to the crew of the Rocinante, and later the Falcon.
- Vestigial Empire: Laconia can still project a great deal of power, but it's clear right from the start that the galaxy-spanning Laconian Empire is dead.
- Wham Episode: "The Lighthouse and the Keeper", where the Preiss gets dutchmanned and then comes back.
