This is not a species entry in the conventional sense. It is a documentation of anomalies. The federation's species registry is designed to catalog entities that interact - with the federation, with each other, or with the environments the federation can observe. Registry number #x is assigned to entities that do none of these things but whose existence can be inferred from physical evidence they have left behind. The designation is an umbrella. It covers an estimated 10-30 distinct entities, though the methodology for distinguishing one from another is disputed and the actual count may be higher, lower, or - in the assessment of a minority of analysts - exactly one.
The "x" in the designation is the standard variable-placeholder character in human mathematics, adopted into federation standard notation because it communicates the right thing: this is a slot in the registry for something unknown, held open because the evidence demands acknowledgment even when identification is not possible. In the notation conventions of other federation species, the same placeholder is rendered in their own mathematical traditions. The meaning is consistent: we know something is here. We do not know what.
The #x designation should not be confused with Species #0, which designates entities whose behavioral patterns preclude cooperative equilibrium. Species #0 entities interact - they defect. #x entities do not interact at all. The distinction is fundamental and is discussed at length below.
In the federation's game-theoretic framework, all species are modeled as agents whose utility functions are interdependent - your payoff depends, at least partially, on what other agents do. This interdependence is what makes cooperation possible, defection meaningful, and the entire apparatus of iterated games applicable. The federation exists because interdependent agents produce better outcomes for all participants through sustained cooperation than through any alternative strategy.
An autarkic agent is one whose utility function is entirely self-contained. Its payoff matrix has no columns for other players. It does not benefit from cooperation, because cooperation implies exchange, and exchange implies that the other party has something you need. It does not defect, because defection implies a game, and a game implies at least two participants whose outcomes are coupled. An autarkic agent's outcomes are not coupled to anything external. It is not playing. It is not refusing to play. The concept of "playing" does not apply, because the game requires interdependence and the agent has none.
This is not Species #0. Species #0 entities are defectors - their utility functions reference other agents, negatively. A Species #0 entity benefits from your loss. An autarkic entity does not reference you at all. The difference is the difference between an enemy and a stranger who does not know or care that you exist.
The #x umbrella covers any entity or phenomenon that meets three criteria: (1) physical evidence of deliberate activity exists; (2) no federation member species or known non-member species has claimed responsibility for or been credibly linked to the activity; and (3) the activity is consistent with an agent whose utility function does not require interaction with other agents.
In practice, the designation covers two broadly distinguishable tiers of evidence that have been grouped under a single registry number for administrative purposes. Whether this grouping reflects a genuine shared category or merely the limits of the federation's taxonomic apparatus is itself one of the open questions the designation is intended to hold.
The majority of entities designated #x are, in principle, comprehensible to the federation's analytical framework. They are species or polities that appear to exist, that appear to be technologically capable, and that have chosen - or whose circumstances have led them - not to participate in the federation or to make their existence formally known.
Evidence for Tier 1 entities includes: anomalous but low-level energy signatures in systems that have not been surveyed at close range; communication signals in formats that do not match any known species' transmission standards but that are consistent with known physics; archaeological evidence of technological civilizations on worlds where no such civilization currently exists; and, in a small number of cases, indirect diplomatic contact through intermediaries or automated systems that has not resulted in sustained interaction.
Tier 1 entities are, in the assessment of the majority of federation analysts, simply non-participants. They are shy, or isolationist, or remnant, or otherwise disinclined to engage with the federation's cooperative framework. Their existence is inferred rather than confirmed, but the inferences are mundane. They are species that do not want to talk to us. The federation respects this, documents the evidence, and maintains the #x designation as a placeholder against the possibility that any of them may eventually choose to make contact.
There is nothing frightening about Tier 1. The galaxy is very large. Not everyone wants to be found.
A subset of #x-designated evidence does not fit the Tier 1 profile.
The distinguishing characteristic of Tier 2 evidence is not that it is unexplained - much of the galaxy is unexplained - but that it implies capabilities that exceed the federation's theoretical models for what a single civilization should be able to achieve without being detected in the process of achieving it. The federation has extensive experience with advanced technology. It has catalogued the engineering traditions of over a thousand spacefaring species across a timespan of millions of years. It has a well-developed sense of what technology looks like, what it can do, and what it costs. Tier 2 evidence falls outside that sense, not dramatically but consistently, in ways that resist reclassification.
Unattributed megastructures. Unclaimed Dyson swarms have been identified in three systems that contain no habitable worlds, no evidence of prior habitation, and no engineering signatures consistent with any known species' construction methods. The swarms are functional, and otherwise uninteresting - many species build Dyson swarms as a matter of course on the path to post-scarcity. These particular Dyson swarms are collecting and storing stellar energy in formats that are not interoperable with federation power infrastructure, nor with any other known energy storage standard. The energy is being collected, stored, and - as far as federation instruments can determine - not used for anything that the federation can detect. The purpose of the collection and the identity of the collector are as of yet unknown.
Gravitational anomalies. In at least fourteen documented cases, long-range survey data has identified gravitational signatures consistent with planetary-mass bodies in systems where, upon closer inspection, no such body exists. The survey data is consistent across multiple independent detection methods. The federation's astrophysics directorate maintains a standing working group on these anomalies and has not reached consensus on an explanation.
Planetary displacement. In a smaller number of cases - three confirmed, two probable - survey data indicates that a planetary body is present in a system where prior surveys, conducted with adequate sensitivity and at sufficient intervals to establish confidence, recorded no such body. The bodies are geologically consistent with long-term formation processes, and they possess stable orbits and typical properties for planets of their size and make. Their presence is, by every physical measure, normal. The prior surveys were thorough, conducted by multiple species using independent methodologies, and are considered reliable.
Black boxes. On at least eighty-nine worlds, artifacts of unknown origin have been identified that do not match any known engineering tradition. These artifacts vary enormously in form, function, and apparent purpose. Some appear to be technological gifts - devices that perform useful functions, left in locations where developing civilizations would find them. Some appear to be monitoring equipment. Some appear to be inert. Some are actively dangerous, and the circumstances of their discovery have, in at least two documented cases, resulted in significant harm to the discovering species. The variation in form is itself significant: if the artifacts share a single creator, that creator reinvents its engineering approach for every artifact, which implies either a cognitive architecture for which consistency is not a value or a deliberate effort to prevent profiling. If the artifacts have multiple creators, the number of independent autarkic entities operating in the galaxy is substantially higher than current estimates suggest.
Engineering style variation. Across all categories of Tier 2 evidence, no consistent engineering signature has been identified. Each artifact, structure, or anomaly appears to have been produced by a different technological tradition. Materials science varies. Design philosophy varies. Manufacturing tolerances vary. This is the single most significant obstacle to determining whether the Tier 2 evidence represents one entity, several entities, or a large and entirely uncatalogued population of autarkic agents. The federation's analytical tools are designed to identify patterns. Tier 2 evidence does not produce patterns, or produces them only at a level of abstraction so high that the pattern may be an artifact of the analytical method rather than of the evidence.
The federation maintains a classification system for artifacts that are large-scale, artificial, and inert: Benign Derelict Objects, or BDOs. The term encompasses any structure of clearly artificial origin that is not claimed by a known civilization, is not currently performing any function detectable to federation instruments, and does not respond to communication attempts. The category is broad by design. It includes objects ranging from sub-kilometer monoliths to stellar-envelope megastructures. The classification carries no implication about the object's origin, purpose, or potential capability; it indicates only that the object is present, unclaimed, and not doing anything.
Most BDOs are, in isolation, unremarkable by federation standards. Artificial satellites of computational substrate. Monoliths of unknown function in stable orbits. Self-replicating probe networks that have completed their replication cycle and gone quiescent - von Neumann architectures are a sufficiently obvious solution to interstellar survey problems that their presence is, in the words of one federation analyst, "about as surprising as finding roads." Three artificial planets have been catalogued, including at least one primarily ceramic megastructure of 1.2 lunar masses with internal volumes and structural features consistent with habitation infrastructure on a scale that defies immediate analysis.
What is notable about the BDO catalogue as a whole is not what it contains but what it does not contain. Human speculative literature of the 20th and 21st centuries - a body of work that has proved unexpectedly useful as a reference taxonomy for hypothetical megastructures - predicted a broad range of stellar- and super-stellar-scale engineering projects: ringworlds, Alderson disks, Dyson shells, Shkadov thrusters, stellar engines, Birch worlds, and structures operating at galactic or supergalactic scales. The federation, with survey data spanning millions of years and a significant fraction of the galaxy's volume, has found none of these. No BDO in the catalogue suggests that any civilization, extant or extinct, federated or autarkic, has attempted engineering at scales above the stellar envelope, with one exception.
In a system catalogued as FDS-9742, approximately 7,400 light-years from Sol, an object has been identified that is, with approximately 80% analytical confidence, a Matriyoshka brain - a stellar-scale, nested-shell computational megastructure that uses the entire energy output of its host star as a power source for information processing.
The object consists of multiple concentric shells of computational substrate surrounding a main-sequence star. The inner shells absorb stellar radiation, perform computation, and radiate waste heat outward. The outer shells absorb the waste heat, perform additional computation at lower energy densities, and radiate further waste heat into space. The thermal signature of the outermost shell is consistent with a structure that is extracting virtually all usable energy from its host star's output and converting it into computation. The object additionally incorporates cheat-space signal architecture in configurations that the federation's own cheat-space engineers have not been able to fully characterize.
It is the single largest artificial object in the federation's catalogue. It is the single largest BDO. It is, by a margin that renders comparison meaningless, the most complex artifact ever documented. No other Matriyoshka brain has been identified, directly or by inference, anywhere in the federation's survey volume. Nothing in the Tier 2 evidence file, or in the federation's broader archaeological record, suggests that any other entity has attempted construction at this scale. The object is unique, and the federation does not have a theoretical framework that adequately explains how it was built without being detected in the process of construction.
The object is dormant. Its computational substrate is intact but not active. No processing activity has been detected. The thermal profile is consistent with a structure that has been powered down for a period that federation astrophysicists estimate at between 40,000 and 200,000 standard years. Its engineering signatures do not match any known species' technological tradition, including the engineering signatures of any other Tier 2 artifact, which is consistent with the general pattern of Tier 2 evidence.
Nobody has attempted to activate it. The reasons for this are not formally documented but are widely understood: a stellar-scale computational structure that incorporates cheat-space architecture in uncharacterized configurations represents, if activated, an information-processing system of sufficient scale and capability that the consequences of activation cannot be predicted with any confidence. The federation's analytical tradition is conservative. The analytical tradition's assessment of this object is that the potential information yield of activation does not justify the potential risk, and that the object's dormant state should be maintained until such time as the federation's theoretical understanding of the object's architecture is sufficient to predict the consequences of activation.
In practice, most species with the theoretical background to understand what the object probably is would prefer that it remain off.
The term - coined by human speculative engineer Robert Bradbury in 1998 AD, approximately 1,030 years before the briefing - describes a class of hypothetical megastructure that human theorists had explored extensively in speculative and academic contexts. The human scientist was able to produce, within hours, a body of pre-reconstitution theoretical literature describing the object's probable architecture, energy budget, computational capacity, and engineering constraints. The literature was speculative. It was also, in the assessment of the federation analysts who reviewed it, substantially correct in its broad predictions.
The editorial board notes that this was not the only occasion on which pre-reconstitution human speculative literature anticipated federation-documented phenomena. The human delegation's familiarity with the concept of self-replicating probes, with the theoretical taxonomy of stellar-scale engineering, and with the implicit threat profile of a dormant computational megastructure of unknown origin was, in the assessment of the federation diplomatic staff present, "unsettling." The human term for the BDO classification - which the delegation's scientific advisor proposed within minutes of being briefed on the catalogue and which was, after some discussion, adopted - was noted by the federation cultural attaché as "characteristically human in that it was simultaneously more casual and more precise than the existing designation."
The federation's #x analytical community is divided, roughly, into three schools of thought regarding the number of distinct entities represented by Tier 2 evidence.
The plurality school holds that the variation in engineering signatures, artifact types, and apparent purposes is best explained by a large number of independent autarkic entities - perhaps dozens, perhaps hundreds - each operating according to its own priorities and leaving its own distinct traces. In this view, the galaxy contains a substantial population of agents that have achieved technological self-sufficiency and independence, and the #x evidence is simply what their activity looks like from the outside. The plurality school considers the question of why so many independent entities would converge on autarky to be an interesting but secondary problem.
The singularity school holds that the evidence is best explained by a single entity - or a single species, or a single polity - that is sophisticated enough to vary its engineering approach deliberately and whose apparent inconsistency is itself the consistent signature. In this view, the engineering variation is not evidence of multiple creators but evidence of a single creator that does not want to be profiled, or that reinvents its methods as a matter of cognitive disposition rather than strategic concealment. The singularity school considers the Matriyoshka brain to be the most significant piece of evidence in its favor, on the grounds that a species capable of building a stellar-scale computational megastructure would have no difficulty producing artifacts in a variety of engineering styles.
The agnostic school holds that the evidence is insufficient to distinguish between these hypotheses, that the analytical methods currently available are not adequate to the problem, and that asserting confidence in either direction is premature. The agnostic school is, by headcount, the largest of the three by a significant margin.
The existence of autarkic agents - entities whose utility functions do not require interaction - poses a question that the federation's cooperative framework is not designed to answer: what does it mean for the federation's model of civilization if some entities have simply opted out of the premise?
The federation is built on the observation that cooperation produces better outcomes than defection for interdependent agents. This is mathematically demonstrable and has been empirically validated across 1,138 member species. But the mathematical demonstration assumes interdependence. An agent that does not need anything from any other agent is not served by cooperation, because cooperation is an exchange and exchange requires mutual need. An autarkic agent has transcended the condition that makes cooperation valuable, which means it has transcended the condition that makes the federation meaningful.
This is not a threat - an autarkic agent that does not need you has no reason to harm you. But it is a limit case that the federation's philosophical tradition has not fully absorbed. The federation's implicit claim - that cooperation is the optimal strategy for most if not all sufficiently intelligent agents - may be true only for agents that remain interdependent, and the #x evidence suggests that interdependence is not a permanent condition. It is possible to outgrow the need for other people. Whether this represents an achievement or a loss is a question that the federation's analytical tradition treats as outside its scope, and that the editorial board treats as the most important question the #x file raises.
The editorial board concludes this entry with a list that is, by the standards of the field guide, unusual: a catalog of questions that the #x file raises and that the federation cannot currently answer.
We do not know how many autarkic entities exist. We do not know whether the Tier 2 evidence represents one entity, several, or many. We do not know what built the Matriyoshka brain in FDS-9742, or why, or why it was turned off. We do not know whether the black boxes found on inhabited and uninhabited worlds share a creator. We do not know whether the planetary displacement events are the work of the same entity or entities responsible for the other Tier 2 evidence. We do not know whether any Tier 2 entity is aware of the federation, or of humanity, or of any individual species. We do not know whether any Tier 2 entity has ever been aware of us. We do not know whether awareness, in the sense that the federation understands it, is a concept that applies. We do not know nor can we infer the bioculture of #x entity(s) - whether they are happy, lonely, sad, spiteful, or mischievous.
The federation documents what it can observe. The #x file is a record of observations that resist interpretation, maintained with the same institutional rigor as every other entry in the registry, in the hope that future analysis will produce understanding that current analysis cannot. In the meantime, the evidence is catalogued, the designation is maintained, and the questions remain open. The editorial board is comfortable with this. Some entries in the registry describe what we know. This one describes the shape of what we don't.