#original worldbuilding

Next part of my Worldbuilding Master's Series! Notable highlights for this section include:

The Civilization Itself

Rise and Development

Collapse and Disappearance

Physical Remnants and Ruins

Forgotten Knowledge and Lost Technology

Historical Memory and Revisionism

Cultural and Symbolic Impact

Exploration and Rediscovery

Survivors, Descendants, and Legacy

Themes of Time, Memory, and Impermanence

No? Me neither!!

The Creators Lore

‼️And your chance to make a character‼️

Welcome to the Longinus Corps!

A short worldbuilding comic I made that's very heavily inspired by Ev*ngelion: Rebuild and FUN facility! Wagner wasn't a properly made OC by then, that's why he's here (with a different persona, ofc!)

Before FUN facility, I was involved and fell in love with a couple facility/supernatural secret corps/LobCorp-esque homebrew RPs. I love the concept so much I just... decide to make my own self-indulgent worldbuild out of it hehehehehhehehehehe.

Nomenclature

Common name: Sylvani (pl.) / Elf (sing.) / Wood Elf (colloquial)

Scientific name: Hominocimex auris-longae Fabricius, 1798

Taxonomy

Kingdom: Animalia

Phylum: Arthropoda

Class: Insecta

Order: Diptera

Family: Sylvanidae

Genus: Hominocimex

Species: H. auris-longae

Note on higher taxonomy: Although H. auris-longae is classified within Diptera on the basis of its winged male caste, adult morphology departs substantially from all other dipteran families. The species is placed here provisionally pending comprehensive genomic analysis. The family Sylvanidae is currently monotypic.

Distribution and Habitat

The range of H. auris-longae is strongly correlated with the long-term population density of Homo sapiens, with whom the species has apparently co-migrated across millennia. The following habitat categories are recognised:

Boreal and temperate forests: Primary habitat. Dense canopy woodland across northern Europe, Scandinavia, Canada, and northern Russia. Populations are largest where forest patches abut established human settlements.

Deciduous woodland margins: Frequently documented at forest edges bordering farmland and villages across central Europe, the British Isles, and the Great Lakes region of North America.

Alpine foothill zones: Smaller, isolated populations in the foothills of the Alps, Carpathians, and Appalachians.

Urban fringe: Males in the pre-deposition scouting phase have been increasingly observed at the edges of suburban areas, and sporadically within cities, particularly during winter months when suitable host households are sought.

Physical Description

Female

Height: 155–175 cm

Build: Slender, upright bipedal stance

Antenna: Slightly pointed and mobile; primary diagnostic character in field identification

Coloration: Muted earth tones (ochre, umber, grey-green); highly effective cryptic camouflage in woodland

Pheromone glands: Highly developed; located in the cervical and thoracic integument; central to reproductive coordination

Wings: Absent in the adult female

Oviduct: Specialised internal oviduct for the production and deposition of eggs following fertilisation

Mating stage: Females construct and maintain a cleared performance space during the mating season; stage fidelity is high across successive seasons

Male

Height: 150–170 cm

Build: Wiry and light-footed; morphology reflects selective pressure for agile locomotion

Antenna: Pointed and pronounced; more conspicuous than in females, particularly post-juvenile

Coloration: Variable; commonly mimics the dress and pigmentation of local H. sapiens populations

Wings: Present; membranous, folded against the dorsum at rest; used extensively during the scouting phase (see Reproductive Behaviour)

Olfactory apparatus: Highly developed; enables long-range navigation by pheromone trail across distances of several kilometre

Reproductive Behaviour

The reproductive system of H. auris-longae is an obligate brood-parasitic strategy executed across a structured, multi-phase mating season. Fertilisation is internal; females gestate and subsequently deposit ovoid eggs. The lifecycle is entrained to human birth rates and seasonal patterns of infant availability.

Phase 1 — Stage Construction

At the onset of the mating season, females select an appropriate site — typically an elevated clearing, a natural amphitheatre, or the root-crown of a large tree — and construct a mating stage: a cleared, sometimes decorated performance platform. The stage may be adorned with moss, pale stones, or shed feathers. Females exhibit high site fidelity, returning to the same stage across multiple seasons. The stage is actively defended against rival females.

Phase 2 — The Mating Dance and Assessment

The female initiates a sustained, rhythmically complex dance display from her stage. Pheromone release accompanies the display, with the emission profile varying in composition and intensity across the dance sequence. Pheromones disperse through the surrounding woodland, detectable to males at distances of several kilometres.

Males approach singly. The pheromone gradient appears to function as a temporal spacing mechanism: males do not arrive simultaneously during the active display phase, and direct inter-male conflict at the stage has not been documented. Upon arrival, a male observes the female’s choreography. If he finds it sufficiently compelling — assessed on criteria including rhythmic complexity, physical endurance, and spatial precision — he joins the display.

The female simultaneously assesses the male: his ability to match her choreographic demands in real time serves as a fitness indicator. If the male fails to maintain pace, coordination, or endurance, the female disengages. A successful conclusion to the shared display indicates mutual selection. Mating follows, after which the male departs the stage. The female resumes her solo display and receives subsequent males across the remainder of the mating season.

Phase 3 — Gestation

Following successful mating, fertilised eggs develop internally within the female’s oviduct. Gestation duration has not been precisely characterised but is synchronised with the broader mating season such that eggs are ready for deposition by the season’s close. Each female typically produces multiple eggs in a given season, each corresponding to a separate mating event.

During the gestation period, the female continues her mating display, attracting and assessing further males. This behaviour is not regarded as incompatible with investment in extant eggs, as the male parent bears no gestational cost and females appear to optimise both egg number and male-genetic diversity within a single season.

Phase 4 — Male Scouting and Pair Maintenance

Following mating, each male enters an extended scouting phase, using his wings and highly developed olfactory system to survey the surrounding landscape for suitable H. sapiens households containing newborn infants. The male assesses household stability, infant vulnerability, and ease of access. Promising sites are marked with a species-specific pheromone deposit that remains detectable to the gestating female over the distances involved.

Throughout the scouting phase, males return periodically to their mating partner’s stage to maintain the pair bond and monitor the progress of gestation. During these visits, information relevant to scouted sites may be communicated through behaviour and pheromone exchange. Males observed during winter scouting — moving through human settlements, often accepting warmth and hospitality — are thought to be the ethological basis for numerous northern European folklore traditions involving gift-bearing winter visitors (see ‘The Gift Season Hypothesis’ under Other Quirks).

Concurrently, males engage in conspecific social behaviour during the scouting phase, including observing other females’ mating displays. This behaviour is not disruptive to existing pair bonds and appears to function as opportunistic mate assessment for subsequent seasons.

Phase 5 — Brood Parasite Deposition

At the close of the mating season, the female deposits her eggs, allocating one egg per target household. She navigates to sites pre-selected and pheromone-marked by her male partners, selecting among candidate sites based on olfactory assessment and prior information. She enters the target household by night and covertly substitutes her larva for the resident human infant.

Sylvani neonates (larvae) are phenotypically indistinguishable from human infants at birth: equivalent in size, skin tone variability, cranial proportions, and vocalisation. The displaced human infant is typically consumed at the deposition site, removing evidence of the substitution. The larva is thus accepted and raised by the foster family without detection.

Phase 6 — Larval Development and Departure

The larva develops entirely within the human foster household. For the duration of childhood and adolescence, morphological differentiation from H. sapiens is minimal. The larva acquires the local language, cultural behaviours, and social mannerisms of its foster family with exceptional fidelity — an adaptation that suppresses detection and reinforces integration.

At developmental maturity, secondary sexual characteristics emerge: the exoskeleton begins to harden visibly at the joints and integument, and the characteristic pointed ears become pronounced as auricular cartilage extends. These changes typically span several weeks and are the definitive morphological signal of adulthood. The maturing individual departs the foster household at this stage, usually during a period of reduced domestic oversight.

Crucially, the timing of the life cycle is self-entraining: a cohort deposited at the close of one mating season reaches developmental maturity precisely at the onset of the following mating season, allowing immediate participation. This tight coupling between the brood-parasite lifecycle and the annual mating season is considered the principal mechanism by which population size remains stable relative to available host families.

Other Quirks and Notable Behaviours

The Convergence Gathering and Polyamorous Bond Formation

In a substantial minority of cases, a female’s established male partners — sometimes the majority of her seasonal cohort — arrive at her stage simultaneously outside the active mating display period. Rather than competing, the males form a cohesive social unit. The female responds by ceasing new mate recruitment, redirecting her attentional and energetic resources toward her existing partners: scouting territories collaboratively on their behalf, and making periodic visits to each male with calibrated gifts (see ‘Gift Economy Between Mates’ below). These convergence groups appear to be lifelong, with no documented dissolution following formation.

Foster-Family Symbiosis

In a minority of cases, an adult sylvani does not permanently leave its foster household upon maturation. Instead, it returns annually, contributing variously to childcare, protection, and resource acquisition for the household. Human families in documented cases consistently describe these returning individuals as benevolent presences, often incorporating them into local supernatural frameworks as protective spirits or good-luck figures. The ethological basis for this behaviour is unclear; a degree of genuine attachment to the foster family, possibly mediated by olfactory imprinting during larval development, has been proposed.

Reverse Brood Pouch Syndrome

A relatively common intersex condition has been characterised in which individuals develop the reproductive anatomy of the opposite sex. An affected male may lack the typical post-mating scouting drive and instead develop egg-producing capacity, while an affected female may develop a functional internal fertilisation organ analogous to the male’s reproductive system. Both configurations have been confirmed as fully functional. Critically, affected individuals also adopt the corresponding mating behaviours: a male with egg-producing anatomy may construct a stage and perform courtship dances, while a female with male-type anatomy may engage in stage-visiting behaviour. These individuals participate in the mating season without exclusion and are not phenotypically distinguishable from unaffected conspecifics until the reproductive phase.

Gift Economy Between Mates

In convergence groups, the female’s gift-giving to her male partners is non-random and appears to reflect active monitoring of each individual’s reproductive state. Males currently gestating—or, in non-standard morphologies, actively engaged in high-metabolic reproductive investment—receive high-caloric food items and soft nesting materials. Non-gestating males receive predominantly symbolic or decorative objects. This differential allocation implies significant social cognitive capacity, including the ability to track the reproductive states of multiple individuals across an extended period and calibrate resource provision accordingly.

Pheromone Memory and Offspring Recognition

Male sylvani demonstrate extraordinary olfactory navigation, capable of locating a specific female’s stage from several kilometres using residual pheromone trails. This same olfactory capacity is sufficient, in principle, to allow a male to distinguish his own biological offspring from human children within a foster household. Whether individual males act on this recognition — and if so, in what manner — remains debated. No systematic field study has directly addressed this question.

Linguistic and Cultural Mimicry

Sylvani are highly capable language learners with an apparent instinct for imitation reinforced by larval development within a human household. Adults returning seasonally to their foster families demonstrate precise acquisition of regional dialects, seasonal ritual behaviours, and local cultural practices. This mimicry is not passive: returning individuals often actively adopt the most current local mannerisms, suggesting ongoing learning rather than simple retention of juvenile-phase acquisition. This capacity is interpreted as an extension of the species’ broader convergent evolutionary strategy: the more comprehensively an individual can pass as human, the lower the risk of detection and removal from the foster household during the vulnerable larval phase.

The ‘Gift Season’ Hypothesis

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