The ''Xeelee Sequence'', by Creator/StephenBaxter, is a sprawling series of novels and short stories all set within the same universe.

In the far future, mankind expands out into a hostile universe, filled with intelligent species as [[StarfishAliens weirdly varied]] as they are [[AliensAreBastards ruthless]]. Above them all, however, are the top dogs of the universe: the Xeelee, the god-like de-facto rulers of the universe. The novels of the "sequence" follow various threads, such as Earth being invaded and occupied by bizarre aliens, or a hopeless war between mankind and the Xeelee, along with various other stories concerning humanity's place in a relatively bleak universe.

Overall, the [[InsistentTerminology Sequence]] is a loosely connected series, covering literally ''billions'' of years of history, with later stories expanding the scope to include literally the entire history of the universe, from beginning to end. The main connecting thread throughout all the novels are the Xeelee's enduring presence and influence on the history of the universe and mankind. The series has a definite chronology, but the novels and short stories were published in AnachronicOrder. However, all of them can be read as individual stand-alone stories.

!!!Novels in the ''Xeelee Sequence'':
* ''Raft'': A group of humans are stranded in an alternate universe where the force of gravity is much stronger.
* ''Timelike Infinity'': Set during a time where Earth has been conquered by aliens. A group of cultists TimeTravel 1,500 years into the past but, rather than warning anyone about the invasion, they follow their own inscrutable agenda.
* ''Flux'': Follows a group of highly-modified humans who live inside a neutron star. A particular severe magnetic field instability, worse than any on record, threatens to destroy their home. To survive, a young woman must travel to a far off city, and eventually outside of the star itself.
* ''Ring'': A generation ship is launched on a thousand-year mission, cruising near the speed of light. Five million years pass in the outside world due to time dilation. The ship arrives back in our Solar System only to find that the sun (and every other star in the observable universe) has aged prematurely into a red giant...something that shouldn't happen for another five '''b'''illion years.
* ''Vacuum Diagrams'' (short story collection)
* The ''Destiny's Children'' sub-series
** ''Coalescent'': In contrast to the other novels, this is set on modern-day Earth, with flashbacks to the age of the Roman Empire. George Poole (father of Michael Poole, a prominent character in the other novels) discovers he has a long-lost sister with ties to an ancient conspiracy.
** ''Exultant'': Set during one of mankind's hopeless wars against the Xeelee, this novel follows a young soldier who pulls off an exotic maneuver in battle which results in him time-traveling into the past and encountering his younger self. The bold tactic pays off and they capture a Xeelee ship. But when they return to Earth, he and his younger self are not welcomed as heroes for their breakthrough but rather tried as deserting criminals (true FromACertainPointOfView) and learn about the dark side of their government.
** ''Transcendent'': Follows Michael Poole's early life, as well as a posthuman woman named Alia who's observing Michael's life half a million years in the future. Michael tries to save the near-future Earth's ecosystem from failing, all the while dealing with mysterious visions of his dead wife. A direct sequel to ''Coalescent'', as George and several other characters show up.
** ''Resplendent'' (short story collection)
* ''Xeelee: Endurance'' (short story collection)
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!!This series provides examples of:
* AbusingTheKardashevScaleForFunAndProfit: The Xeelee have absolute mastery over the entirety of all baryonic matter in universe. Entire galactic clusters are just bricks to these guys.
** Future humans make it to Type III and try to attack the Xeelee by shooting a ''whole neutron star'' at them like a bullet. The Xeelee brush this off as though it were insignificant... because it absolutely was. In the endgame of the war between the Xeelee and the Photino Birds, the Xeelee used hypermassive knots of cosmic string as missile-to-missile defense against ''weaponized galaxies''.
** There's also [[spoiler:the Photino Birds, creatures of dark matter against whom the Xeelee fight a multi-billion year existential war and '''lose''']], who have absolute mastery over all the ''dark matter'' in the universe (which outmasses regular baryonic matter by about 9 to 1), because they ''are'' the dark matter in the universe. [[note]]The ''real'' unbeatable advantage, though, is their mastery of ''time''. They can live [[StableTimeLoop infinitely long]], can temporally duplicate themselves at any time (defying NeverTheSelvesShallMeet), and can travel anywhere, any''when'' instantly. Basically, they pervade the entire timeline of the universe, forwards ''and'' backwards; the only way to beat them is to work ''outside'' of time, and not even the Xeelee can do that.[[/note]]
* AcePilot: Jim Bolder, hence his being entrusted with a [[CoolShip Xeelee nightfighter]] by the Qax, with bad results. [[NiceJobFixingItVillain For]] [[DecapitatedArmy them.]]
* AliensAreBastards: Played straight with some species. Averted ([[BlueAndOrangeMorality more or less]]) with the Xeelee, who go out of their way to prevent extinction of other sentient lifeforms, even humanity, which repeatedly attacked them.
** Also averted with the Silver Ghosts, who are much less aggressive than [[HumansAreFlawed humanity]] (except the [[DarkIsEvil Black Ghost]]) but unfortunately end up in the path of the Third Expansion.
* AnachronicOrder: The publication order of the stories does not correspond at all to the chronological order in which they happen.
* AntiVillain: The Xeelee have such a [[BlueAndOrangeMorality bizarre]] morality due to their TechnologicalSingularity and [[TimeAbyss obscene age]] that it's impossible to say if they're even truly malevolent towards races they dislike.
* BigDamnVillains: The [[spoiler: Qax]] are tricked into fulfilling this role at the end of ''The Baryonic Lords'', distracting the photino birds long enough for the last of humanity to escape through the Ring.
* BigDumbObject: The novels feature an object called "Bolder's Ring", built by the titular aliens; it's constructed out of the remains of ''galaxies'' (and is revealed to be the cause of the RealLife [[http://en.wikipedia.org/wiki/Great_Attractor Great Attractor]]) and is essentially a black hole that has been stretched into a one-dimensional loop millions of light years in length. It's eventually revealed [[spoiler: to be an escape route for the Xeelee from the Universe, by means of tearing a hole in spacetime through the middle of the ring via the unimaginably strong gravitational forces created through its rotation]].
** Also, the "Sugar Lump" - a perfect cube the size of a small moon, which appears to serve no purpose whatsoever. [[spoiler: Later is revealed to be one of many identical devices which sent the Xeelee back in time to essentially create themselves using a StableTimeLoop]].
* BittersweetEnding: [[spoiler: The Xeelee ultimately [[TheBadGuyWins lose against the Photino Birds]] and the universe as we know it ends. However in one last act, the Xeelee give the remnants of humanity and others a vessel to escape to a new universe where they can hopefully build civilization anew.]]
* BizarreAlienBiology: Qax biology is based around chemical cycles embedded in convection cells. A Qax is composed of millions of such cells that exist in any kind of turbulent fluid (water, air, gas giant, star, [[spoiler:space-time]]). In short they’re highly organised, living storms.
* BizarreAlienSenses: The modified humans in ''Flux'' 'see' sound waves which are transmitted through the Air (their term for the neutron superfluid in the neutron star), 'smell' photons that can only diffuse slowly in the Air, and 'hear' temperature fluctuations.
* BlessedWithSuck: Sometimes a pharaoh's children are born with Qax immortality. But they don’t all grow - they stop developing, at the age of two years or one year or six months or a month; some of them even stop growing in the womb and have to be aborted.
* BondVillainStupidity: The [[AliensAreBastards Qax]] could have saved themselves a lot of trouble if they had simply exterminated humanity.
* CallASmeerpARabbit: To the tiny {{Artificial Human}}s that inhabit the neutron star in which ''Flux'' takes place: 'Air' is the neutron superfluid in which they live; 'plants' and 'animals' are, respectively, the sessile and mobile indigenous lifeforms of the star (the 'plants' are in turn divided into 'trees' and 'grasses'); 'wood' is the building material made from the 'trees'; 'leaves' are the edible appendages of the 'trees'; 'wheat' is the 'grass' cultivated for food ('bread'); 'Air-pigs' are the main 'animals' used as livestock; 'Air-boars' are the savage cousins of the Air-pigs; and there are also 'animals' called 'spin-spiders' and 'rays.
* ChildSoldiers: Most of the main characters in ''Exultant''.
* ClothesMakeTheSuperman: In ''Hero'', the amazing powers of the eponymous superhero comes from his suit.
* ColonyDrop: There's the extreme colony drop option where a Neutron Star is accelerated to high fraction of light speed and smashed into Bolder's Ring (see BigDumbObject above).
* ContinuityNod: Near the end of ''Ring'', Louise and Spinner visit the same neutron star as the setting of ''Flux'', and later, before [[spoiler:the ''Great Northern'' passes through Bolder's Ring, its crew has a brief glimpse at the alternate universe depicted in ''Raft'']].
* CoolShip: Xeelee nightfighters, which can travel at near-lightspeed even before they fire up their hyperdrive, by flapping wings made of folded space-time.
* CrapsackWorld: Millions of years of humanity in a massive HopelessWar of attrition against the Xeelee [[spoiler: who are also fighting a race of dark matter beings who want to render the universe unfit for baryonic life (like humanity)]]. [[spoiler:They lose. First the humans, than the Xeelee.]]
** [[spoiler: Well, at least the Xeelee not only managed to get the hell out of the doomed Universe, but also provided means for at least the remnants of humanity to escape. While some refugees from our Universe ended up in one that was practically unfit for human life, this wasn't any of the known evacuation groups, so there is at least some hope for the humanity...]]
* DistantFinale: The final chapters of ''Timelike Infinity'' take place five million years in the far future, after [[spoiler:Michael Poole is trapped there due to the destabilisation of the wormhole interface]].
* EldritchLocation: ''Raft'' is set an alternate universe where the gravitational force is a "billion" times as strong as our own. Stars are only a mile across and have extremely brief lives, becoming cooled kernels a hundred yards wide with a surface gravity of five g. Humans possess a "respectable" gravity field in and of themselves.
* {{Egopolis}}: The capital of the tiny humans in ''Flux'', Parz City, shares its name with Jasoft Parz and Luru Parz, two humans who collaborated with the Qax regime.
* EvilVersusEvil: In the finale of ''The Baryonic Lords'', Paul tricks the [[spoiler: photino birds into thinking the Xeelee are returning, leading them to aggressively ramp up their destruction of the Ring. The genocidal Qax remnants - who have been waiting patiently to exterminate the last humans - have a collective "oh shit" moment and lead a last ditch attack on the birds at the Ring so that they can escape the universe. The humans use the confusion of the battle to sneak through the Ring, escaping both the Qax and the slow death from the machinations of the birds.]]
* TheFederation: In ''The Sun-People'', which is set in AD 3672 during humanity's early expansion, it is directly assumed that the human incursions into the asteroid where the story happens will automatically halt when it comes into conflict with other, and vulnerable, intelligent life. That, combined with the sketched out detail of an array of governments and institutions to be navigated, give a very different feeling that the stories set under the totalitarian, xenophobic, rapacious human regimes in the later stories.
* FlatCharacter: The story generally doesn't have much interest in its characters, with people being important only insofar as they've connected to current ideologies, current economic realities, or certain modes of scientific inquiry.
* ForeverWar: The Xeelee are nearly immortal, and humanity quickly proves itself a race of consummate survivors. They don't like each other. Do the math. But even that [[spoiler:pales before the Xeelee-Photino war]].
** Mankind vs. Qax. Infuriated by their improbable repulsion from an enslaved earth, and further goaded by humanity [[spoiler: being indirectly responsible for the destruction of their home system]], the Qax bear their grudge so long that it becomes a ''species imperative'' (i.e. eat, breathe, breed, destroy all humans).
* GeniusBruiser: The tribelike mannerisms of the Boneys from ''Raft'' hide minds well-versed in orbital mechanics to rival trained scientists.
* GuileHero / MagnificentBastard: Jim Bolder.
* HigherTechSpecies: The Xeelee are an extreme example. Despite being "only" this trope (because their universe-shattering technology ''is'' recognizable as such), they could absolutely run rings around quite a few examples of SufficientlyAdvancedAliens from other works.
* HoistByTheirOwnPetard / NiceJobFixingItVillain: Thank you so much for discharging the star-disrupting gun right next to your own sun, [[spoiler: [[WhatAnIdiot Qax]]]]!
* HumansAreWarriors: In spades, at least once the "[[NonindicativeName Interim Coalition of Governance]]" comes into power. The Xeelee outclass Humans in pretty much every sphere of technology, but the FantasticRacism of Mankind's "Third Expansion" era doesn't let a little thing like ''that'' stand in the way of galactic conquest. A line in ''Exultant'' expresses humanity's tenacity as such:
-->''To the Xeelee, we were little more than rats - so that's what we became. Tenacious, relentless, swarming; fighting an interstellar war with teeth and nails.''
* HumanSubspecies: Especially so in ''Flux'': Humans have been modified to microscopic lifeforms to live within a Neutron Star.
* ImAHumanitarian: The big secret of [[spoiler:the Boneys]] in ''Raft''.
* InsufficientlyAdvancedAlien: The HiveMind StarfishAliens known as the Squeem conquer Earth, despite being no more intelligent and not much ''older'' than humans. How? They lucked out on finding technology left over from the [[SufficientlyAdvancedAliens sufficiently advanced]] [[{{Precursors}} Xeelee]].
* IntangibleMan: [[spoiler:Michael Poole]] after the encounter with the "Anti-Xeelee".
* LensmanArmsRace: The Xeelee use cosmic strings to build a [[OurWormholesAreDifferent wormhole]] (dubbed by humans as "Bolder's Ring") in order to [[spoiler:escape into another universe]]. The Ring is so massive that it's gravity well is pulling in ''galaxies'' from all directions towards it at high speed. The Xeelee's antagonists one up on this by meticulously [[spoiler:arranging galaxies around the Ring in just the right pattern to form a gravitational resonance that will shake the Ring apart]].
* LivingRelic: Following the Qax occupation, this is the argument used by the pharaohs (humans who collaborated with the Qax and were gifted immortality in return) to dissuade the new human government from killing them: they have become the last keepers of the history and lore of humanity and the planet Earth, which were largely erased during the Qax's Extirpation.
-->'''Gemo Cana:''' Everything humans know about the Xeelee today, every bit of intelligence we have, was preserved by the pharaohs. I refuse to plead with you for my life. But I am concerned that you should understand. We pharaohs were not dynastic tyrants. We fought, in our way, to survive the Qax Occupation, and the Extirpation. For we are the wisdom and continuity of the race. Destroy us and you complete the work of the Qax for them, finish the Extirpation. Destroy us and you destroy your own past – which we preserved for you, at great cost to ourselves.
* LivingShip: The Spline are immense, space-faring creatures who engineer themselves to be spacecraft and then hire themselves out to other species.
* LongevityTreatment: Anti-Senescence technology, which repairs genetic damage due to age via nanobots. The treatment has a 99% success rate, though failures typically end with a terminal illness. Lifespan with AS treatments theoretically has no upper limit, though in practice the treatments begin to break down at 400-500 years.
* LukeNounverber: The primitive people of the jungle on the ''Great Northern'' have names like Arrow Maker, Spinner-of-Rope, Trapper-of-Toads and Painter-of-Faces.
* MileLongShip: The Xeelee Nightfighter has "wings" that stretch out for kilometers, though the cabin is rather small.
* MonumentalDamage: Stonehenge is mostly lost in space near the end of ''Timelike Infinity'', except for a single megalith which becomes a satellite of Jupiter.
* MultiethnicName: The initial crew of the ''Great Northern'' are named Serena Harvey Gallium Harvey Milpitas, Mark Bassett Friar Armonk Wu, Louise Ye Armonk and Garry Benson Deng Uvarov.
* NoDeadBodyPoops: Implied aversion in ''Raft''. One character sees "a shape hanging from rope" and "a pool of something brown and thick" beneath it.
* NonIndicativeName: The "Interim Coalition of Governance" actually rules humanity for an "interim" period ''over 20,000 years long.''
* ObliviouslyEvil: The photino birds set out to transform all stars into white dwarfs, which would cause the eventual extinction of all baryonic life forms, including humans. Despite having goals that are hostile to us, photino birds do not seem to be malevolent. In fact, they are most likely unaware that there are baryonic life forms, because their own form prevents them from noticing us at all or realising that the ageing of stars has unfortunate effects to the baryonic universe. Any attempt to communicate them was fruitless.
* PoorCommunicationKills: Humans start a massive war with Xeelee because they believe that the Ring is intended to wreck the Universe. Unforunately, they discover too late that it's actually [[spoiler:a wormhole created by the Xeelee as the only way for baryonic life to escape extinction at the hands of the unstoppable Photino Birds]]. Similarly, the [[spoiler:Photino Birds]] are so alien that they most likely do not even realise that they are [[spoiler:wiping out untold numbers of species in the process of making the Universe more comfortable for themselves]].
* RapidAging: During her brief life as a human, Lieserl's body is engineered by nanobots that cause her to age rapidly. Memories and learning are also implanted into her cortex. The combination of these effects results in Lieserl living the equivalent of a 90-year life in 90 days.
* RealityWarper: The "Snowmen" technology used to protect Earth in the short story "The Siege of Earth" (from ''Resplendent'') seems to at least border on this.
* RedSkyTakeWarning: One of the indicators that the nebula in ''Raft'' needs to be evacuated.
* RuleOfCool: Celestial bodies up to and including entire galaxies used as [[ColonyDrop projectiles]]? Megastructures millions of light years across? Handguns that can destroy ''stars''? Aliens altering the value of Planck's constant simply in order to build a faster computer? Creator/StephenBaxter was rocking this trope before it was mainstream.
* ScienceMarchesOn: Virtually inevitable given Baxter's heavy reliance on speculative physics. For example, recent results from the Large Hadron Collider appear to have refuted at least the simplest variants of supersymmetry, rendering the science behind the Susy drive depicted in 'The Quagma Datum' far more dubious.
* ScryVsScry: Humanity fights a War against the [[StarfishAliens Xeelee]] over the Milky Way Galaxy where both sides can send information backwards in time using [[FasterThanLightTravel FTL]]. In practice, neither side can ever get an advantage. This goes on for [[HopelessWar tens of thousands of years]].
* ShadowArchetype: [[AvertedTrope Averted]] with the "Anti-Xeelee", since its name actually refers to the fact it travels backwards in time, like some anti-particles are theorized to do. The antagonists of the Xeelee, the [[spoiler:Photino Birds]], fit.
* SingleBiomePlanet: The homeworld of the Qax is a swamp planet, covered from pole to pole by an ocean.
* SonOfAnApe: By the time of ''Exultant'' humanity has converted almost the entirety of the Milky Way into an industrial war machine with which they are engaging in a multi-millenial pan-galactic campaign against the Xeelee. Still, the Xeelee view this as roughly the equivalent of an especially persistent cockroach infestation, and think of humanity as little more than pond life.
* SpaceWhale: The Spline are [[LivingShip giant living armored spaceships]] that evolved from alien whales. They live off interstellar gas and other species use them as transports and warships.
* StableTimeLoop: It's eventually revealed that the Xeelee [[spoiler:sent themselves back in time to supercharge their own development]]. Then it turns out [[spoiler:the Photino Birds can go one better. They do this ''naturally and at will'', even from the end of the universe back to the beginning.]]
* StarfishAliens: Pretty much every single race in the series. There's almost nothing remotely human-like, aside from humanity's descendants-- [[TranshumanAliens if then]].
* SufficientlyAdvancedAliens: The Xeelee are sufficiently mysterious in-universe that no one is sure what they really are. Though their actual power far exceeds many other examples that are the traditional sufficiently advanced alien, in many of the earlier short stories the reader is given the impression they are normal biological lifeforms. This is simply because their godlike technology is still recognizable as such and uses comprehensible interfaces, if not comprehensible principles; they're a hyper-extreme example of HigherTechSpecies instead. However:
** There are indications that Bolder's impression of the Xeelee were retconned, or at the very least the Nightfighter he piloted was a second-hand cast off, like so much of Xeelee technology. In ''Exultant'', it is revealed that the Xeelee are self-aware space-time constructs that have existed since very earliest moments of the universe.
** The Anti-Xeelee definitely ''is'' sufficiently advanced, in a DeusEstMachina sort of way.
* SuperBreedingProgram: Garry Uvarov's eugenic program, which aims to improve the human stock by getting rid of late acting lethal genes, which normally could never be selected out of the gene pool because they only kill old bodies after they have reproduced. Uvarov orders his followers to live as hunter-gatherers in the sealed off forest, abandons Anti-Senescence treatments and bans reproduction before the age of 40, with this limit being steadily raised over the years. After eight centuries, the jungle folk's average lifespan goes up from 100 to 250, with the 80-year-old Arrow Maker being in the prime of life.
* SuperPersistentPredator: The Squeem missile sent to destroy an asteroid engineered by some humans to be an escape hatch off the occupied Solar System in ''Pilot''. Among the pursuit, the missile adapts itself to accelerate faster, the humans have to modify their ship to do the same. This continues on, moving significant distances for what is millions of years outside due to time dilation. By the time they manage to crash the missile into a black hole, the humans have abandoned their physical forms, and Squeem rule over humanity has long since ended, that the chase continues past the point where there are probably any other humans still alive.
* ThirdPersonPerson: Quid from ''Raft''.
* TimeAbyss: The traitorous humans who collaboratorated with the alien who conquered Earth were given eternal life as a reward. They eventually begin [[WhoWantsToLiveForever to regret this]].
-->''My name is Luru Parz. I was born in the year AD 5279, as humans once counted time. Now I have lived so long that such dates have no meaning. We have lost the years, lost them in orders of magnitude.''
* TimeSkip: The first part of ''Ring'' ends with the launch of the ''Great Northern'' in AD 3951. The second part starts after nearly a thousand subjective years on the ship, which equals five million years outside due to time dilation.
* TrappedInThePast: By the end of ''Timelike Infinity'', [[spoiler:Jasoft Parz and Shira, two humans from AD 5407, are trapped in AD 3717]].
* TreeVessel: In ''Raft'', one of the strange lifeforms in the high-gravity universe is a species of mobile floating trees. Humans turn them into vessels and steer them through space.
* {{Unperson}}: The alien Qax attempt to do this to the entire history of humankind, in a project know as the "Extirpation", in order to make humans more docile slaves.
* WaveMotionGun: The Xeelee starbreakers, which shoot focused gravity waves that can tear apart stars or cause them to go nova, certainly qualify. By the time of ''Exultant'', humanity also uses guns which fire magnetic monopoles and later black holes.
* {{Xenofiction}}: A few of the short stories set in the Expansion era in ''Vacuum Diagrams'' are partially told from the point of view of the aliens.
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