Kaiju and the Hollow: Creature Codex

The codex of hostile, non-mortal, and near-mortal creatures of Sulamir and Merretia. This document catalogues what walks, crawls, swims, flies, or seeps in where it is not wanted. For the metaphysical basis of the Wound and the Hollow from which most of these entities derive, see and

Creatures are grouped by origin and register. Within each group, entries are arranged by scale or by first appearance.

1. The Taxonomy of Origin

The creatures of this world come from a small number of origin categories. A given encounter should be classifiable by origin, because the origin determines what can kill it, what it costs to kill it, and what killing it costs.

Hollow seepage. Entities that leak through the Wound when the local fabric of reality thins. They are not individual beings in the ordinary sense; they are something closer to the visible shape of a wound. See section 2.
Hollow-summoned. Entities deliberately called through by a Hollow practitioner. Larger, more coherent, more individual than seepage. See section 3.
Kaiju. Entities grown in the Wound over long periods, or crossed through at enormous scale. Rare, catastrophic, civilizational threats. See section 4.
Sea-horrors. Creatures of the Maw and the West Sea. Not necessarily Hollow-origin; many are ancient native predators of the deep that the sinking of Aldasen exposed to shallower waters. See section 5.
Aldasenian undead. The Aldeken. Transformed inhabitants of the fallen city. See section 6.
Native predators and beasts. Ordinary dangerous fauna of Merretia. Cataloged for completeness. See section 7.
Angel-demon-era constructs. Machines or magical entities left over from the Founding, some dormant, some wandering. See section 8.

A given creature may have a double origin (a Founding-era construct animated by Hollow seepage, for example), in which case it is listed under its dominant classification with a cross-reference.

1.1 The party-facing bestiary and the roleplaying vocabulary

For play (the tabletop game and the module bestiaries), the recognizable monsters of the roleplaying tradition are the design vocabulary for Merretian creatures, refracted through the origin-taxonomy above so each keeps this world’s logic instead of the generic one. The rule of thumb: the creatures that feel wrong, that should not exist, that carry cosmic dread, are Hollow-manifestations (seepage, summoned, or kaiju), absences borrowing a familiar shape. A thing a player would recognize as a beholder, a mind flayer, a gibbering aberration, a shambling horror, or a fiend is, in Merretian truth, the Hollow wearing that costume: an absence given a shape the mortal eye can hold, the same compression by which the true forms of angels flatten into wings and daemons into horns. They are never a someone (section 2A.3); the familiar silhouette is a borrowed mask over a hole.

Not every monster is Hollow, and the taxonomy sorts the rest so the distinction stays sharp. Native beasts (section 7) supply the ordinary dangerous fauna a party fights with no cosmic weight (the giant rats of a one-shot are exactly this, mundane and displaced, not the Hollow, which is the very hinge the Cold Lamp module turns on). Aldasenian undead (section 6, the Aldeken), the peoples, and Founding-era constructs (section 8) each give a different, non-Hollow source for a creature a roleplaying eye would file under one label. So a single monster-manual entry can carry several Merretian truths at once (a “zombie” is a Hollow-revenant, an Aldeken, or a Yulnesh person, depending), which is a feature rather than a conflict: the origin is the real content, and the familiar name is only the costume.

The design rule: reach for the recognizable creature the players expect, then assign it an origin from the taxonomy, and let the origin, not the silhouette, decide what it is, what kills it, and what killing it costs.

2. Hollow Seepage

Where the Wound is locally thin, something comes through. Seepage is the most common category of Hollow-origin manifestation and the category the OCTA considers the most diagnostic: recurring seepage in a location is the clearest sign that the Wound is widening nearby.

2.1 The Unseen

The folk name for the invisible creatures seen in the Steam Tunnels at the opening of the main-line series. See for the scene canon.

Appearance. Nearly invisible to ordinary vision. A defender in combat with the Unseen will see their own strike land on nothing, see their own blood appear on surfaces without cause, and feel the impact of a creature they cannot locate. Close observers have reported a faint refraction in the air where the Unseen stand, as though a lens of heat had settled there, but most fighters never notice it in the press of engagement.

Visibility by discipline. The Unseen are visible, with no difficulty, to practitioners with strong Order-sight. Oen sees them plainly. A skilled Binder might see the outline of their structural presence. A Current-user might read their electromagnetic absence (the Unseen do not reflect, refract, or emit light in any ordinary way; a Current-user attuned to the local field reads them as a hole). A Knowing-practitioner with the thoughtplayer technique can share another practitioner’s sight of the Unseen into ordinary minds, which is the tactical resolution used in the opening arc. See

Scale and behavior. Roughly human-scale. Move with a deliberate intelligence that is not quite animal and not quite conscious. Seek warmth, living tissue, and concentrations of bonded pair-energy (which makes human settlements the obvious target). They do not pack-hunt in the traditional sense, but they arrive in small numbers together, suggesting that the Wound opens for multiple at once rather than one at a time.

What hurts them. Ordinary weapons land physical blows and damage them, but only when the wielder can see where to strike. Order disciplines bind and destroy them cleanly. The Heart current does not affect them (they have no emotion to seize). The Knowing current does not read them (they have no mind to share). They can be killed. They can also withdraw back through the seam they came from if they are not pressed.

What their deaths leave. Unseen corpses dissolve into something between vapor and absence within minutes of death. A skilled Order-practitioner can read the dissolution faintly. Ordinary observers cannot. This means that after an engagement the physical evidence vanishes, which is part of why the Unseen have been able to enter the Steam Tunnels without the city above registering their presence.

Metaphysical reading. The Unseen are not beings. They are the visible consequence of the Wound being locally thin enough to let something leak through. Killing an Unseen does not reduce the Wound. Pressing the Unseen back through their seam, as an Order-practitioner binding them out, does reduce the local thinning. This distinction is important tactically: the goal of a defense force is not to accumulate a body count but to close seams.

The seepage is orchestrated. The Steam Tunnel seepage at book one opening is not ambient widening; it is the visible end of a deliberate Hollow operation conducted by the Heralds of the Sunborn under Valareth (the returned Zar Valareth, operating behind the cult mask). The Heralds have spent years preparing the working: locating a strategic point in the dome’s metaphysical floor (the Rhydin levels beneath the Steam Tunnels, where the pre-Founding masonry creates seams the dome’s binding cells were never written to reinforce), introducing the local thinning gradually, and timing the breach to test the dome’s vulnerability. The seepage is both a test (does the dome stop Hollow incursion at the metaphysical layer?) and a lure (an in-dome breach this significant will surface unregistered practitioners; the Heralds want the data those responses generate, including practitioners outside the academy gate and any cosmologically anomalous figures who register on their watch). The metal-armed prescient Herald is the operational figure on the ground in Sulamir, conducting the test and reading the response in real time. The Iosan Serpents are the partial counter-force; their counter-operation is one of the threads the band’s investigation eventually crosses. The reader does not learn the Heralds connection at book one’s open; the band’s investigation surfaces it across the descent, with the full reveal landing at the climax or the close.

First appearance. Opening arc,

2.2 Lesser seepage forms

2A. The Hollow: Nature, Seams, Detection, Closure, and Voice

Cosmological grounding: sections 6-7.

2A.1 Nature

The Hollow is not a place, a power, or a will. It is a defect in the weave of reality: a region of the un-paired phase that predates relation, trapped inside the otherwise-bonded fabric the way a vortex is trapped in a superconductor. The Source-Companion bond was the condensation of the substrate into relational order; the Wound is where that condensation failed to close; the Hollow is the persisting un-closed remainder, inside the world rather than beside or beyond it. It has no address of its own, no self, and no god, because a self and a god each require a closed loop of relation, which is exactly what the Hollow is the absence of. It cannot want. It is the shape of a wanting that never happened.

Why it externalizes cost. Every lawful working bills a bonded counterparty on the far end of a relation. The Hollow has no far end, so a cost run through it has no creditor and settles on whatever relation stands nearest: a pair-bond, a body, the weather, the ground. Globally this accretion is the widening of the Wound. Locally it is what becomes a seam.

2A.2 The seam ladder

Three states, distinguished by how much the ground remembers:

A puncture. Ordinary Hollow-work: opens and closes with the working, mostly recovers, widens the Wound by a fraction. A wound dressed once, healing crooked.
A proto-seam. Three openings logged at one point (the OCTA’s threshold, and not mere bookkeeping): the site stops fully recovering, a focus stone flickers dark unprompted near it, animals avoid it before people know why. The place has begun to keep the shape of the door.
A seam. The locus stops recovering at all. Passage goes ambient, needing no practitioner to stay open; the tear is load-bearing in its own right. This is the Steam Tunnel condition.

Three routes open a seam:

Accumulation. Repeated Hollow-work, or repeated relational failure, at one locus. The Heralds’ deliberate method, and the folk version (a place where oaths keep breaking, a battlefield revisited by grief).
A single catastrophic working. A greater summoning or archon-scale event tears the fabric in one motion. The likely route for a true kaiju crossing.
Severance. Breaking a load-bearing bond widens the Wound directly, because it undoes a mend, with no stone ever going voided and no Hollow discipline in the chain of custody. This is Kane’s route. Stacked at one lineage, severance alone can open a seam through grief and betrayal: a family that keeps breaking at the same address until something is standing in the room that was never invited. It is the route no instrument flags.

A seam can be engineered. It does not require ambient neglect, only patience and a floor plan: years of deliberate thinning at a structurally weak point, faster and more controllable than waiting for accumulation. This is what the Heralds did beneath the Steam Tunnels (section 2.1).

2A.3 What crosses, and detecting it

What crosses is never a someone. Not gods, angels, or daemons, which relate. What comes through a seam has behavior but not desire: it seeks warmth, living tissue, and concentrations of bonded pair-energy, but the seeking is a pressure differential, not a want. Relation is the thing with no counterpart on the Hollow’s side, so proximity to relation is where the gradient is steepest, and what looks like hunting is a vacuum finding the nearest place to fill. A bonded party draws seepage the way a lit window draws moths. Because the Hollow has no shape of its own, everything that crosses borrows its coherence from whatever is nearest: a dead animal’s body, a summoner’s remembered face, the echo of a severed bond, or, at worst, a living practitioner worn from the inside (see 3.3).

Detection: the bill, not the color. The one question under every OCTA reading is whose door the cost arrived at. Lawful work bills the practitioner; Hollow-work bills the world. The tells:

On a stone. Full void reads coarsely at a distance: the stone drinks both light and ink, a hole in the visual field, which is the correct positive signal for a channel with no relational completion, not a blank. Finely, a Knowing-adept reads the stone’s history: a lawful stone’s saturation events correlate with its bearer’s own eroding interior, while a Hollow-touched object returns no coherent bearer-side ledger, because the cost was never written into a person. Reading the Knowing at a voided object is itself a Hollow-drift: the instrument is a door, an ontological risk, not a procedural one.
On a site. A place where events cohere less well than they should, where luck bends without a bender.
On a corpse or survivor. The absence of the wear a working life should have left, a practitioner too whole against a documented history of practice, because long-term Hollow-users do not retire, they go away and something comes back wearing their face.
On a living practitioner mid-working. Eye-flash and stone-color, near-unfakeable, since the color is coupled to a circuit that either completes or does not.

Where detection fails. Three surfaces the OCTA cannot reliably read, each a story engine:

Passive faith-leakage. Unclaimed faith drifting into the Wound with no conscious user produces no stone, no eye-flash, no practitioner. Diffuse and civilizational; no instrument catches it at the individual scale.
The single extraordinary Dream-shunt. A stone under that load may flicker toward void without fully voiding, an ambiguous reading a trained Reader can misjudge either way.
The Dream-cover. The Dream’s own highest working is built to resemble the thing the OCTA hunts, because it does a leashed version of the same act, so a master dreamwalker and a Hollow-cultist wearing indigo present nearly identically at a glance. Only the slow tracing of where the cost actually landed, in an eroding selfhood over time, tells them apart, and slowness is the one thing a frightened institution never has. This gap produces both of the OCTA’s characteristic injustices: legitimate dreamwalkers burned, and patient Hollow-workers hidden for years behind a Dream cover. See for how the OCTA’s field practice degrades this into certified-versus-uncertified.

2A.4 Closing a seam, and the one thing that closes it faster

Killing what crosses closes nothing; it was never a being whose death was the relevant event. Pressing a crossing back through the tear is Binding-work, and it stops the immediate incursion, but it does not re-knit the locus. True closure means binding the locus itself, not the visitor: sustained, communal, nuclear-tier Binding performed at the tear. It is catastrophically costly (sun-tier energy, paid in the closers’ own bodies) and it mostly fails, because a seam offers structure nothing to grip; the closer stands nearer the door than anyone and risks becoming the borrowed shape the Hollow lacked. True seam-closures are historic and rare, and require several master nuclear-Binders in concert.

The one tool that changes the odds. The Relational Principle runs both ways: severance widens the Wound, and integration mends it. So a closure worked alongside a bond sincerely and publicly mended at the very place a bond once broke closes a seam faster and holds it longer than Binding alone. This is the exact inverse of Kane’s severance, performed on purpose, and it is a real mechanic available to a closure team, not a sentiment laid over the work.

2A.5 The Hollow has no voice (craft ruling)

The Hollow cannot speak with a voice of its own, structurally and permanently, because a voice is what a closed self-relation sounds like from outside and the Hollow is exactly where that closure never reached. If it ever produced a stable voice, it would by that fact have become a new archetype, a mend condensing at the seam, and stopped being Hollow. Two things may speak in a scene, and never a third:

Ventriloquism. The borrowed voice of a hollowed person, saying true things in a register that curdles them. It must never monologue, never explain a plan, never announce a grievance. The moment it does, it has become a person with motives and stopped being the Hollow.
The doctrine, before any seam opens. The tempter’s argument, severance is liberation, in a living and sincere and often loving mouth (Aesen Corveliss is the type case). This is where the real danger lives: not in what crosses, but in the idea that reaches a practitioner, a cultist, or a grieving lover and makes cutting a bond sound like freedom. Bad theology leaks into the Hollow as unclaimed faith, and doctrine congenial to it leaks back out to find carriers. Give the argument to the tempted living; let the absence, when the reader finally meets it, be met as absence.

3. Hollow-Summoned Entities

Entities deliberately called through by a Hollow practitioner. Larger, more coherent, and more dangerous than ordinary seepage. These require a specific summoner, a specific ritual, and a specific widening of the Wound at the summoning site, which means every summoning leaves a trace the OCTA can sometimes find.

3.1 Minor summoned entities

Servants, familiars, and small combat-capable beings called through by mid-tier Hollow practitioners. They tend to wear borrowed forms: the body of a recently killed animal, the outline of a person from the summoner’s memory, a figure assembled from available matter. They are individually dangerous but defeatable.

3.2 Greater summoned entities

Beings called through by high-tier Hollow practitioners, usually in cult ritual. These can approach kaiju scale. Every greater summoning is a civic-scale event that the OCTA, the guilds, and the religions collaborate to answer.

3.3 Hollow-possessed practitioners

The endpoint of a Hollow practitioner’s own career. The practitioner who uses the Hollow for long enough eventually becomes a vessel for what they were opening doors to. They may still walk, speak, and pass for themselves for a time. They are not themselves anymore. When such a one speaks, it is the practitioner’s own voice, borrowed and worn thin, saying true things in a register that curdles them. It is not the Hollow speaking, for the Hollow has no voice of its own (section 2A.5), and it must never be written as a monologue.

Recognition. Other high practitioners can usually tell, though they may not be able to prove it. Dream-walkers recognize them instantly. Cyl, as archon of Chaos, reads them as wrongness in the room. Oen reads them as geometry that does not close.

Disposition. Possessed practitioners are treated as Hollow cultists in the eyes of the law. Execution without trial is the standard response once the possession is confirmed.

4. Kaiju

The civilizational-scale entities. Entities grown in the Wound over long periods, or crossed through at scale. Rare, catastrophic, and the historical context for most of the great defensive alliances between guilds.

4.1 The general premise

Kaiju events are not ordinary combat. They require coordinated response by multiple guilds, often by the great houses, and sometimes by the religions in concert. A kaiju-level event that cannot be stopped reshapes the continent. The fall of Aldasen was the last event of this scale in the historical memory of the guilds, though the Aldasen catastrophe was caused by the lich-king rather than by a kaiju in the strict sense.

A kaiju is not a someone. It is the same absence that makes an Unseen, held coherent at enormous scale for a long time, whether grown slowly in the Wound or crossed through in one catastrophic working. Scaling up does not give it an interior. It gives it weather: a gravity that warps the behavior of everyone near it and reads, from underneath, as a will bearing down on them. That is a trick of scale and human narrative instinct, not a change in kind. The thing folklore says sleeps at the floor of the Long Rent is not angry; it has no register in which anger is available. Write the giant absence as absence, never as a monster with a grievance (see 2A.5).

4.2 Expected kaiju

Candidates:

A deep-sea kaiju of the Maw, distinct from the Kravilith (which is a colony-sea-horror, see section 5).
A kaiju associated with the Long Rent, perhaps the “something enormous” folklore says sleeps at its floor. See
A kaiju that emerges from the Steam Tunnels themselves if the Unseen seam is not closed quickly enough, an escalation-tier creature that the opening arc is positioned to set up but that does not manifest until later in the series.
A kaiju summoned deliberately by a Hollow cult in the climax of the first or second trilogy.

The specific roster will be locked when scenes require it.

5. Sea-Horrors

Creatures of the Maw and the West Sea. Not all are Hollow-origin; most are ancient native predators the sinking of Aldasen brought to shallower waters and closer to human shipping lanes.

5.1 Kravis

Small, tentacled, individually dangerous. Attack ships, divers, and small expeditions. A single Kravis is survivable by a hardened fighter. A swarm is not. See for the original notes.

5.2 Kravilith

A colony form. Many Kravis melded into a single gigantic creature. Witnessed in the Maw. The Kravilith can be defeated by (a) feeding it a vessel, (b) exposing its brain (Haymond’s Scorpion move has been documented to do this), or (c) using Rodasan devices to clear the sea floor so an expedition can drop below it. Encounters are rare and expensive.

5.3 Fire Snakes

Small monsters that merge into a larger Salamander form. Predate on sailors and adventurers along particular West Sea coasts and near Aldasen. Their heat is physical rather than elemental; they can be frozen or starved of oxygen.

5.4 Other sea-horrors

6. Aldasenian Undead

6.1 Aldeken (Wight / Zombie)

The transformed inhabitants of Aldasen. Made by the lich-king Zar Valareth during the fall of the city. Many are crazed beyond recognition. Some retain fragments of speech and even memory, and, if killed cleanly, have been known to thank their killers. These latter are the more tragic members of the category; an Aldeken who can still speak one’s own name is the worst thing some Sulamiri veterans ever encountered.

Origin. Not Hollow. Zar Valareth’s transformation magic was a synthesis of the Unmaking, the Dream, and a trained use of the Faith directed toward himself. Killing an Aldeken does not widen or narrow the Wound. It simply grants a long-delayed death.

Disposition. Aldeken are executed on sight with the dignity an Aldeken in lucid moments would request.

6.2 Lucid Aldeken

The rare Aldeken who retain most of themselves are a subcategory that some scholars treat as a distinct entry in the codex. A lucid Aldeken can be reasoned with for short periods before the lich-touch reasserts. Historical records include a small number of lucid Aldeken who, in the decades after the fall, attempted to warn living Sulamiris about specific Zar Valareth operations before the residual magic forced them silent. The records are fragmentary. The Core archives are rumored to hold more complete material.

7. Native Predators and Beasts

Ordinary dangerous fauna of Merretia. Listed for completeness and because some are mistaken for Hollow-origin creatures and wrongly feared, while others are under-feared because they look like ordinary beasts.

7.1 Canyon beasts of the Long Rent

7.2 Alpine predators of the high provinces

7.3 Steam Tunnel fauna

Rats, tunnel-cats, blind fish, and the lesser burrowers of the city’s underside. None are Hollow-origin. All are ordinary fauna adapted to the tunnels. Oen grew up alongside them and considers them cohabitants, not threats.

8. Angel-Demon-Era Constructs

Machines or magical entities left over from the Founding. Some dormant, some slowly re-awakening, some wandering.

8.1 Sealed vaults

The angel-demon-era vaults beneath Sulamir sometimes contain constructs: weapons, guardians, animate machinery. Most remain dormant. Disturbance (usually by a guild expedition or a thief) can wake them. Waking one is a major civic event and sometimes a major crime.

8.2 The Center Spire systems

The Center Spire contains Founding-era systems that have not been opened in generations. Some of these are believed to be sentient at the scale of the system itself, rather than at the scale of an individual entity.

8.3 Wandering constructs

Occasionally a Founding-era entity is discovered walking loose on the continent, activated by an unknown cause. These are classified by the OCTA as “loose constructs” and responded to by whichever guild has the nearest response capacity.