Liminality and Imposition

How the Realms interact when they touch

The Realms are not separate the way planets are separate. They drift through the foundations of existence, occasionally overlapping, frequently brushing against one another, sometimes passing through each other entirely for stretches of mortal time. Where they touch, reality becomes contested.
Two mechanisms govern these interactions. They are related but distinct, and the distinction matters.

Liminality

A state of affairs. Two or more Realms occupying the same space.
Liminality is what happens when Realms overlap. It is not a collision — Realms cannot destroy each other by proximity. It is coexistence under conditions of contested rules. Within a Liminal zone, two ontologies are simultaneously asserting themselves, and what is "true" in that space depends on which Realm's logic is currently dominant.
Most contact between Realms occurs during Liminal events. Most contact between mortals and the supernatural occurs because a mortal has entered a Liminal zone without realizing it. A house where a tragedy occurred may have become slightly Umbral; a place where Faith is concentrated may be partially Celestial; a crossroads where promises have been made for centuries may have drifted into Arcadia. The mortal Realm does not announce its overlaps. Most mortals walk through Liminal zones every day without noticing.
Example: A child's nightmare manifests in a subway tunnel. The tunnel has become Liminal with Umbra — belief and imagination are temporarily as real as the concrete and the rails. The nightmare is not metaphor; it is a being with weight. The Liminality ends when the overlap recedes, and the nightmare either retreats into Umbra or, if conditions sustain, persists.
Liminality can be brief — seconds — or it can last for centuries. Some locations are permanently Liminal because the geometry of the cosmos has settled them at the edge of two Realms. Jack's Tavern is the most prominent example: it sits at a deliberate Liminality of Arcadia, the mortal Realm, and several others, by design and by the materials Jack chose for its construction.

Imposition

An action. A being carrying their home ontology into a foreign Realm.
Imposition is what happens when a being brings the rules of their home Realm into a Realm where those rules are not native. The being is not entering a Liminal zone — they are creating one, locally and temporarily, by force of their own presence.
A Celestial working a miracle on Earth is imposing Celestia onto the mortal Realm. The miracle is not "supernatural" in the sense of breaking physics; it is Celestial logic temporarily overriding mortal logic in the space immediately around the miracle. A fey speaking binding words to a mortal is imposing Arcadia: the words mean what they mean in Arcadia, and the mortal is bound accordingly, even though they are standing on ground where Contract is not the default physics.
Example: A mortal scholar confronts an ancient nightmare from Umbra. She does not flee, and she does not fight in the way the nightmare expects. She imposes the Iron Nexus on the encounter — observing the nightmare, measuring it, naming its composition with the precision of data. In Umbra, to be fully known is to be diminished. The nightmare's nature is incompatible with the mortal's framework, and it recoils. The scholar has not used magic. She has used another Realm's way of being, brought into this one through her own preparation.
Imposition is always temporary, always local, and always costs the being something — Faith, effort, conviction, ontological strain, depending on the Realms involved. The deeper the imposition, the more it costs. Sustained imposition is exhausting and, in some cases, impossible.

Liminal Beings

Some beings are themselves Liminal — existing not in one Realm with the ability to impose on others, but at the intersection of multiple ontologies simultaneously. They are not visiting Liminality; they are Liminality, carried in a single body.
Such beings are rare. They have access to the logics of every Realm they are native to, without the cost imposition normally requires. They are also subject to all those Realms' rules at once, which is its own kind of burden. The most prominent example is Elias the Traveler, who is four-times Liminal and has walked between Realms for nine thousand years.
For the full account, see Elias's own article — forthcoming.

Why This Matters

Liminality and imposition are not background mechanics. They are the engine of nearly every supernatural event in mortal history.
Every ghost a mortal has reported is a Liminal phenomenon — typically the mortal Realm overlapping briefly with Umbra, or with the alchemical fire of destroyed Sheol. Every prophecy that proves accurate is a moment when Nirvana's spiraled time has touched the mortal Realm. Every binding oath that holds when no court could enforce it is Arcadia imposing through the speaker. Every miracle, every curse, every place that "feels" wrong without explanation, every dream that proves true: these are the Realms touching.
Mortals have, for as long as there have been mortals, observed these touches and developed traditions to describe them. Norse seidr observed Umbral and Arcadian phenomena and unified them into a working practice. Vedic philosophy mapped Ruskenn through Liminality at scale. Vodou's crossroads work observes the same threshold dynamics that make Jack's door function. Each tradition is partial, none is wrong, all are useful.
The supernatural is not a violation of how reality works. It is reality working in more than one way at once.

The Law of Conservation of Ontology

Coined by Anna Dalca during her work on cross-ontological methodology.
The host Realm's rules reassert themselves over time.
This is the principle that governs every imposition and bounds every Liminality. A Celestial miracle on Earth does not persist forever; the mortal Realm reasserts its logic as the imposition fades, and the miraculous becomes ordinary again. A fey binding spoken outside Arcadia weakens as time passes, unless the binding is renewed or anchored. A nightmare manifested from Umbra into the mortal Realm requires belief to sustain itself; in the absence of belief, the mortal Realm's rules reassert and the nightmare dissolves.
This is not a punishment or a defense mechanism. It is simply how the cosmos balances itself. Every Realm's logic is the default within its own borders; outside those borders, the logic must be actively sustained against the resistance of whichever Realm is currently the host. Conservation of Ontology is the cosmos refusing to let any single Realm dominate any space it does not natively occupy.
It has practical consequences:
Miracles cost Faith. The Faith is not a fee — it is the energy required to sustain the imposition against mortal-Realm conservation.
Contracts decay outside Arcadia. A binding spoken on Earth weakens; a binding spoken in Arcadia does not. Long-term mortal Contracts often require periodic renewal or an Arcadian anchor.
Voracian predators respect the Contract at Jack's Tavern. Not from courtesy, but because Jack's Arcadian rules are imposing on them, and the cost of resisting that imposition in a place where Arcadia is fully operational would be ruinous.
Mira Khoury dissolves a nightmare with skepticism. Skepticism is the mortal Realm reasserting against an Umbral imposition. The dissolution is conservation operating through her.
The Law applies to everyone. Gods, demons, mortals, the Tulasi, the Iron Nexus, Ruskenn. No being has been exempted. No method has been found.

Liminality and Imposition