Event chains

An eerie story written by the British writer Alexis Kennedy and introduced in the update 1.4, Horizon Signal is the longest and most complex chain in Stellaris. It is very rare and can bring massive changes to an empire's species. The event cannot happen to AI empires, so there is no risk of losing the opportunity by expanding too slow.
When a new game is started, there is a 5% chance for the Horizon Signal event to activate in a random uncontrolled black hole system. It should be noted that the systems containing the Infinity Machine and the Dimensional Horror can never trigger the event.
Worm in Waiting: Signals[]
The Horizon Signal story begins with the The Worm-in-Waiting: Signals event chain, which can be triggered by a science ship with a scientist assigned to it entering the correct black hole system.
The Horizon Signal

An alert communications officer has identified what appears to be a faint signal, almost lost in the gamma-ray flashes from the black hole here - faint, but unmistakably artificial. This raises intriguing possibilities for our scientists.
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Is triggered only by:
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OK
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The Horizon Signal: GRAVITY IS DESIRE

Science Officer [scientist name] reports that the signal was unexpectedly easy to decipher... but the team has spent considerable time confirming that it was not a hoax. It is a repeating, half-coherent message in the [empire adjective] language - something like a poem. It repeats the phrases GRAVITY IS DESIRE and TIME IS SIGHT. It encodes co-ordinates near the black hole. And it ends with a dedication by name to the Science Officer - who adds dispassionately that they have confirmed that the signal has been radiating into interstellar space before their birth. It fact, the signal may predate our civilization.
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Fascinating! Send the vessel to those co-ordinates!
This is a trick, or a trap. Log it and move on.
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The Horizon Signal: THE WORM![]() As the [science ship name] approaches the co-ordinates specified by the signal, it begins to report spatial distortions and curious lensing effects - a rich stream of valuable data. Then the transmission becomes distorted. What happens next is analyzed exhaustively.
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The Horizon Signal: - message ends -![]() [scientist name] complies, with a mixture of reluctance and relief. Their psych report later indicates that they are subject of recurring nightmares - of impossible labyrinths, of hungry vertigo of interstellar space, of their names being called in the dark. Within a homeworld year, the message has ceased.
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The Horizon Signal: REPRISE

The black hole in [system name] is active again. Once again, a looping signal flickers in the darkness at the edge of normal space. But this time, there's an acoustic message encoded in the signal. It sounds very much like [lost scientist name]'s voice. "What was shall be," intones, "what shall be was.". Then the same co-ordinates as the first signal, the co-ordinates where [lost scientist name] was lost - what the media christened "the Exit Point". Then they say a name: [scientist name].
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[scientist name] volunteers to go. Permit it.
Permit them to go, but rig their ship's drive to detonate.
Not this time. Ignore it.
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The Horizon Signal: I'm Through![]() This time, the ship is running fully automated. [scientist name] is the only crew-member aboard. As it approaches the Exit Point, the telemetry stream fills up with fascinating data. Once again, space flexes, gravity uncoils. [scientist name] reads off the headline data, echoing the telemetry. They are commendably calm: we've sent a professional. It takes a little while for anyone to realize that something is peculiar about the timing.
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The Horizon Signal: An Intervention![]() This time, [scientist name] is the only crew-member aboard. The ship is running fully automated... and its systems are programmed to detonate the drive once conditions match those immediately prior to the last ship's disappearance. As it approaches the exit point, the telemetry stream fills up with fascinating data. Once again, space flexes, gravity uncoils. [scientist name] reads off the headline data, echoing the telemetry. They are commendably calm: we've sent a professional. It takes a little while for anyone to realize that something is peculiar about the timing.
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The Horizon Signal: THE TRINE THE QUINE THE TRINE![]() Once again, the Horizon Signal in [black hole name] is active. It has upped its game. Once again, the transmission includes the Exit Point's co-ordinates. It's signed with the private comm keys of [first lost scientist name] and [second lost scientist name]. But this time it's a generative text program written in an elderly programming language that creates what appear to be love poems - love poems directed to [scientist name].
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The Horizon Signal: A Lesson in the Ashes![]() We've reproduced conditions that approximate those around the black hole. We've found that the fragments we recover cycle between states, in ways that should be impossible - as if time were oscillating. We can derive energy from this - although there are worrying changes to local spacetime.
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The Horizon Signal: Where the End Comes from

This will be the end of me," [scientist name] says at the briefing before launch. "I know I won't come back. But I think I always knew this would happen. Whatever is in the hole has been waiting for us for a long long time - I think it's been waiting for me, since before I was born.".
Once again, the single-pilot ship approaches the Exit Point. Once again, space boils like a fever. Again, our sensor arrays soak up fascinating data. This time, [scientist name] is silent. The telemetry becomes intermittent; and then it, too, is silent. The ship has reached the Exit Point. The conditions around it are returning to normal. Nothing has happened.
Nothing? The monitoring team mutter furiously. The ship is different... in fact, it's a different ship. It's [first lost scientist name]'s vessel, lost these years past, drifting now away from the Exit Point. A salvage team finds it pristine and empty - no trace of crew, and no sign of violence. But there's a journal entry in [first lost scientist name]'s name, titled WHAT WAS WILL BE. Our scientists review it nervously. "Impossible," one says. "I hope so," says another.
The ship is renamed the "Foundling" and returned to service. The Signal, dead or sleeping, says nothing at all, ever again.
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And yet, this may not be the end.
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The Loop Temple: Signs in the Stone

Archaeologists have found a forgotten temple in the remote highlands of [capital name] - buried for centuries, but recently exposed by an earthquake. Dating techniques suggest it's a pre-industrial relic, hand-hewn from volcanic rock. However, the recurring symbol on the walls and radial altar - a Möbius-looped serpent consuming its own tail - has no obvious precedent in our early history, and the inscriptions use an unknown alphabet. One excitable archaeologist suggests it's a relic left by an unknown precursor race.
In a presumably meaningless coincidence, the quake seems to have occurred at the same time as the final message from the black hole in [black hole system name].
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This merits study.
Ominous.
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The Loop Temple: Time and Stone

Our scientists have learned a great deal about the subterranean temple, but some questions remain. A roof aperture, along with the radial altar, suggests it was once a solar calendar; but it's so badly damaged by the earthquake that we can't be certain. If the builders found particular dates important, we'll never know which ones. We've had better luck with the "unknown alphabet." It's a debased variant of a better-known hieratic script - not an alien language at all - and we've successfully deciphered it. The temple is dedicated to the "Waiting Worm" or the Worm-in-Waiting. Most of the inscriptions are sonorous, poetic invocations requesting its appearance or, if read in the other direction, its departure. There is also a body of inscriptions describing the "operations of the universe," which our more excitable archaeologist swears contains references to advanced field equations - nothing new to us, but very impressive for a temple of this vintage. We have yet to find a physicist who's prepared to go on record as agreeing that the references are meaningful, though.
The temple holds no cosmic secrets or alien weapons, as far as we can tell. But its dark spaces have a distinctive, menacing beauty, and the poetry of the invocations to the Worm-in-Waiting becomes fashionable. They are set to popular music; they are published in collections.
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Open the Loop Temple to the public.
Reserve the Temple for academic study only.
There is something wrong here. Show leadership by sealing the Temple. |
Optional events[]
Optional events can only take place after the initial event chain but before the Omega Alignment building has been constructed.
The Messenger: WHAT WAS, WILL BE

The [science ship name] has located a small, minimally powered artificial object, broadcasting a looping signal at local range only. These sorts of things usually turn out to be escape pods, and this looks like one of those. It's been out here a long time.
When the crew cracks it open - carefully observing quarantine procedures - they find ancient remains, preserved by the sterile pod environment. So far, not unusual. The captain of the [science ship name] indicates, however, that they did not expect to find the [empire adjective] words WHAT WAS, WILL BE; WHAT WILL BE, WAS daubed on the wall in the bodily fluids of the pod's occupant - who the crew are now wryly referring to as the Messenger. They add that there are some equally unexpected anatomical similarities between the Messenger's species, and our own.
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Interesting
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The Messenger: Possibilities

We've established that the escape pod was the kind of commercially available knockoff common in the previous phase of galactic civilization - no new technologies or other insights. The remains of the Messenger, however, are another matter. It's unmistakably an ancestor or a variant of the [main species adjective] species. Perhaps we have cousins out there - or perhaps we were subject to genetic manipulation by a precursor race. [Society research leading scientist name] is requesting permission to conduct more extensive research.
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No. And [Society research leading scientist name] must release their existing research.
Release the funding.
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The Messenger: Unleashed![]() [Society research leading scientist name] has reconstructed the Messenger species. It's feebler than ours, but has significantly improved cognitive abilities. There is some confusion about whether we were the source species, and the Messenger the modified version, or whether the Messenger was our ancestor. It is a little embarrassing to imagine that we might be descended from such an effete species - but [Society research leading scientist name] is firmly of that opinion. Indeed, they consider the loss of cognitive abilities a "tragedy.". Such a tragedy that they have undergone a retroviral treatment to alter their own physiology to that of the Messengers. They insist that this will equip them much better to continue the project.
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The Messenger: Leashed![]() [Society research leading scientist name] has reconstructed the Messenger. It's, ah, quite impressive - worryingly so. It seems to be considerably more robust and aggressive than our current edition. There is some confusion about whether we were the source species, and the Messenger the modified version, or whether the Messenger was our ancestor. [Society research leading scientist name] is firmly of the former opinion - that we were once much more of a warrior species, and that some meddling precursor muzzled us genetically. Indeed, they consider the loss of our martial abilities a "tragedy." Such a tragedy that they have undergone a retroviral treatment to alter their own physiology to that of the Messengers. They insist that this will equip them much better to continue the project.
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The Messenger: A New Light![]() [Society research leading scientist name] has now recreated the genetic heritage of the Messenger species. Without stopping to ask anyone's opinion, they have also created highly contagious retroviral agent. It stalks our worlds. Under its influence, our primary species falls into a chrysalis-coma and emerges a day later as the Messenger species. This is causing, it is fair to say, some excitement.
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The Messenger: Night Falls![]() [Society research leading scientist name] has now recreated the genetic heritage of the Messenger species. Without stopping to ask anyone's opinion, they have also created highly contagious retroviral agent. It stalks our worlds. Under its influence, our primary species falls into a chrysalis-coma and emerges a day later as the Messenger species. This is causing, it is fair to say, some excitement.
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A Rendezvous

The [fleet name]'s name is being hailed...by the Syzygy of [empire name]. This, despite the fact that it isn't sending any ID codes we recognize, and no ship of that name has ever been commissioned. The Syzygy's commanding officer claims to be Captain [commander name].
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Hm. Our commander of that name is alive, well and elsewhere.
This *must* be an ambush. We're taking no chances. Battlestations.
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A Rendezvous: How it Ends

A Rendezvous: The Captain that Will Be![]() [commander name] is silent in the days that follow. It is no small thing to hear that you are already dead. But in time that silence becomes a determination, and an almost reckless confidence.
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A Rendezvous: Interference![]() A static-speckled message comes from the captain of the "Syzygy". Behind them, the bridge is wreathed in smoke. "Too late," they cough. "You left it too long. The Loop won't forgive me. Please -" The message ends there.
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A Rendezvous: The Day and the Hour

In the years that follow, there are reported sightings of commander [commander name] across [empire adjective] space and beyond. When a celebrated leader dies, this kind of thing is not unknown, of course; and they had become a kind of legend since the Syzygy Rendezvous. But we can't be sure.
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We may never know. Oh, we can be sure. |
The Coils of God

Our observation station on [planet name] reports the rise of an unusual minority religious-artistic movement, the Coils of God. Primitive mechanical clocks are considered holy, but ritually destroyed after a year's operation. The worm- and serpent-analogues of the planets are protected from harm. Time, the Coils-priests say, is a labyrinth. "What was, will be; what will be, was" they intone in their prayers.
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This sounds familiar. Observe it as closely as we can. This sounds familiar. Suppress it as best we can. |
The Coils of God: a Subtle Persecution![]() We've convinced native rulers that the Coils of God cult on [planet name] is a threat. The Coils-priests have been discouraged, imprisoned, or, regrettably, incinerated. Pre-FTL species have access to a deep well of hatred and suspicion: there are times when that's very useful.
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The Coils of God: Deep Roots![]() We've convinced native rulers that the Coils of God cult on [planet name] is a threat. The Coils-priests have been discouraged, imprisoned, or, regrettably, incinerated. But the cult is tenacious, and our observers express concerns that it may just have gone underground.
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The Coils of God: the Labyrinth Ceremonies

The Coils of God cult on [planet name] has grown with unusual speed. It can be found in every city on the planet, and it's fostering a series of lengthy ceremonies conducted by citizens in every walk of life. The whole species has taken to them with unlikely enthusiasm. The rich adopt elaborate circular dances for their celebrations. The poor daub complex looping sigils on their doors. Even playground games are chants about the circular nature of time.
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This is unsettling. Intervene to shut it down, but subtly.
This is serious. Use force to shut it down, whatever the risks.
Fascinating! Send a team to study the rites - to participate, if possible.
Primitives do primitive things. Continue to observe. |
The Coils of God: Ceremony's End![]() Our campaign of subversion has disrupted the Coils of God ceremonies on [planet name]. The nobility abandon their cult. The looping graffiti on walls fades. The young return to playground games about flirtation, murder and other healthy childhood pastimes. There is a rash of suicides among Coils-priests. If there was a crisis, perhaps it is past.
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The Coils of God: The Blood of Priests![]() Our operatives are merciless. They abduct or assassinate every Coils-priest they can find. They set demolition charges on houses bearing the mark of the Loop. [planet name] is alive with rumors that the Coils' blasphemy has aroused the wrath of a greater god. Before long, the natives are beating the Coils-priests to death without any assistance from our operatives. The observation team is horrified; but if there was a crisis, it has been averted.
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![]() Our ethnographers are fascinated by the complexity of the ceremonies. They hypothesize secret communication channels, steganographic prayer-encodings, or algorithmic underpinnings to the rituals. In fact, they're returning preliminary evidence of this last when their communications abruptly cease. In fact, all communication seems to have ceased, planet-wide. Reports from satellites and survey craft flyovers confirm: there is no activity on the planet at all. No vehicles moving on the road, no emissions or thermal signatures in population centers. No signs of life... And here's the final report. The entire [primitive species name] population of the planet - including your ethnography team - is absent, with all the business of a sudden but not violent exit. Meals were left unfinished, pets unfed, the occasional house aflame from an unattended stove. Gravitational anomalies were recorded at the assumed time of departure. In almost every street, the looped chalk sigils of the Coils bear witness.
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The Waiting World

It appears this was not the first [main species name] settlement on this planet. A number of facilities and residences have been carefully moth-balled and, with a little restoration, will serve our new colony well. But all records have been erased. Possibly this was a smugglers' port, or a haven for political exiles.
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Excellent! Make arrangements to restore the buildings. This is too good to be true. Demolish the districts.
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The Waiting World: Demolition![]() Our engineers set charges and retire to a safe distance. The buildings are reduced to ruins. Eventually, the ruins will crack and crumble to boulders, pebbles, dust, under the assault of wind, roots, rain. But their shell will endure for centuries yet; and there will be stories, we'll hear, of shadows in the stone by day, blue lights by night. Our colonists will avoid them. They'll attract no visitors.
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The Waiting World: Shadows in the walls![]() Our settlers were initially happy to make use the buildings on [colony name]. Their existence jump-started the colony. But now they've grown nervous. There are rumors that the buildings may still have occupants, or active security systems, although no evidence of either has been found. Some colonists insist, enigmatically, that there are "shadows in the walls." |
The Waiting World: Too Many

Interesting news from [colony name], where we found those abandoned buildings. A census shows too many settlers. Records on a new colony are always unreliable, but as far as we can tell they have authentic citizen IDs - and no-one on the world has suggested there are any mysterious strangers. But the birth rate must have been extraordinarily high, or we have unlicensed migration, or... something. Somehow, the population is higher than we might reasonably expect.
The Waiting World: And They Still Come

Another update from [colony name], where we found those abandoned buildings. The number of colonists continues to increase, and now we're finding irregularities in the records - family groups that shouldn't exist, birth dates that make no sense. There must be secret migration from a lost colony, or else some peculiar sabotage by the colonists.
The Waiting World: Everyone Is![]() Further unlikely news from [colony name], where the population had been mysteriously increasing. Population numbers are now what we'd expect, but there has been some sort of information sabotage, or... or what, our administrators aren't really sure. None of the individuals on the planet exists in our records. Every original colonist is missing. It's as if they've all been replaced by complete strangers. As against that, they all swear they're loyal citizens of [empire name]. They're all productive and apparently sane. In all communications they deny all knowledge of any confusion, and insist there must be a mistake at our end.
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The Waiting World: Exit![]() An abrupt and total communications blackout from [colony name]. We somehow had too many people there. Now, it appears, we have no-one at all. The entire population has simply vanished overnight. Have they left the world? Gone into hiding? Engaged in planet-wide genocide?
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The Waiting World: Everything and Nothing![]() Our team reports that the population of the planet are healthy, normal and apparently bewildered by all the fuss. There are some peculiarities, though. An unusual number of multiple births; a planet-wide idiosyncrasy where no-one has any regard for punctuality; and fluctuations in local solar radiation that are characteristic of pre-supernova stars. They also observe a number of "luminosity events" on the surface where light somehow appears to be accumulated and released by prismatic functions of the atmosphere. This is valuable and peculiar data. But it could be coincidental. If anything has happened to the colonists, it remains a mystery.
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The Waiting World: the Purge![]() This may have been a terrible crime. Or it may have preserved our nation from something even worse. The population centers of [colony name] seethe beneath the energies of our weapons. When we are done, every building is glowing rubble; no living sapient remains. }} |
The Waiting World: the Quality of Light![]() Our team reports that [planet name] is, indeed, empty - not only of colonists, but of any sign the colony was ever there. The buildings are gone, the satellites and orbital structures are gone, the atmosphere shows none of the footprints of technological civilization. In the words of the team, it's as if the entire planet has been reset. They also report fluctuations in local solar radiation that are characteristic of pre-supernova stars - and a number of "luminosity events" on the surface where light somehow appears to be accumulated and released by prismatic functions of the atmosphere. This is valuable and peculiar data. But it doesn't clarify the fate of the colonists.
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Omega Alignment events[]
Entropic Recursion and
Doctrine: Strange Loop are prerequisite for a rare technology called the
Omega Theory. Researching it grants access to a unique building, the Omega Alignment, that can only be built on the empire capital to bring the end of the event chain.
The End in the Beginning

There is a consciousness outside time and beneath space. It is a labyrinthine tangle of desire and desperation. Our remote ancestors knew it as the Loop, the Worm-in-Waiting. We have met it out there, where the void is tormented by gravity. It seems to have taken a personal interest in us. There are mathematical proofs that it loves us, but love to the Worm is not like love to anything that subsists in ordinary space.
With all we have learned, we think that we might be able to use the Omega Alignment to open an access route - an Entry Point - for the Worm to manifest in our home system. (The Worm is fond of beginnings, and this is ours.) What consequences would that have? We have yet to find anyone who's prepared to commit to an answer. Immortality, perhaps, or apocalypse. But we would certainly learn a great deal.
Trigger conditions: | Is triggered only by:
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Perhaps the Worm loves us, and perhaps we could love the Worm.
This is not a safe experiment. But we could learn so much.
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The Heart of the Sun

The Project is complete. The accelerators are online. The power network of a dozen cities is diverted to wake the pseudo-singularity at the heart of the Alignment. Space shudders like wind-wracked cloth. [star name], for a heart-stopping moment, dims, and then brightens. A shadow coils in its heart. The Worm is here. It unfolds like origami.
Across the system, sensors shut down in abject disbelief as the incomprehensible data of its arrival sleets through them. On the homeworld, our subjects scream and cower as they feel its attention turned up on them, and upon us. It presents a wordless question - or rather, we have become aware that this question was always what it was asking us, every time we encountered it.
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YES. Whatever it requires, we consent.
NO. We have brought it here to learn, and if need be, defeat it.
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The Future![]() The Worm loves us. It will always love us, and thus it always has. It winds around the hot heart of our home star. It winds around every infinitesimal loop of genetic information. It provokes a shuddering series of cataclysms in the planetary crust of our home, but when our star grows cold, that cataclysm will warm us. We understand so much more. We will always be what we were going to be, wound tight in the love of the Worm.
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The Shattered Loop![]() The Worm came in through the boundary fences of spacetime like a hungry predator, or a jilted and furious lover. It's still out there, and wherever it is, no doubt it's angry. But you have the incandescent shards of its avatar to hoard and to study, as a cosmic trophy. Other empires will know what you have achieved today.
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