The crepuscular process is understood as the vespers’ judgment made manifest. After all, a “crepuscule” is just a vesperbane whose vespers no longer abide by the pact which binds vesper to bane.

There’s four chief ways for this to happen.

Affliction

Essentially, this is vespertine cancer. Sometimes your vespers just get sick, profoundly sick, and shit goes badly wrong

Contradiction

You break too many oaths (or the fundamental oath, the septagrammaton), and are punished.

This one is usually pretty boring; mostly the vespers just eat you, or sometimes they eat your noucardium[A Mind Like a Massacre] and turn you into a mindless animal, perhaps influenced by their will

Malediction

Haruspices can achieve this various certain high level curses. Nasty stuff, but pretty similar to the above

Transgression

This is what we’re really concerned with. A transgression is when you do something that’s not technically against any oaths (well, some translations of the septagrammaton are pretty broad…), and so the vespers hotfix a judgment.

Vespers are not bugs, and they refuse to make themselves clear to bugs (deliberately so, many think‍ ‍‍—‍ they’ve been exploited by bugs, and if their workings were clear, they’d be more exploited), but there’s a few categories of thing that get the vespers to raise their hackles.

World-ending threats

This is believed to be the reason for the crepuscule of Dlann, the archtitan, which resides in the Obliteration Fields EZ.

Vesper tampering

New means of breeding vespers are often excluded, as are attempts to meddle in the fundamental nature of vespers. (Famously, this is the theory that explains the Bogs of Eden EZ, as well as lesser known instances like the easily-confused pair of Meta-Vesper Interdict and Mega-Vesper Interdict.)

Ichor virulence

This is a difficult theory to rigorously formulate, because one must explain why plagues and myxogoths aren’t excluded. But there’s a certain compelling similarity between the Black Pudding EZ (infamous failed myxogoth breeding experiment), the Hemotechtonic EZ (the titan Tzic’zahd’s attempt to pump magma through her veins), and the

Nouetic influence

this explains the smiting of God-empress Oosifea (though theorized, the National Henosis EZ has never been discovered), the Whalesong EZ, and the abominable City of Eels.

Unchecked growth

// FIXME: I don’t have examples offhand, but I can imagine some crazy fungus growth would go here.

A question one might ask is: why crepuscules? If vespers don’t like a technique, why not stamp it out entirely? Why set aside a few square miles where it can run free?

After decades of theorizing and debate, one of the most compelling explanations is compromise. Sure, vespers “want” to punish the bane who transgressed against their vision, but every bane is host to number of vespers. Those vespers have what we might call “rights”.

Crepuscules are rarely sudden things. To the vespers, endowments are beautiful things, and the tools that culminated in some transgressive technique might’ve been the work of years, their entire life’s work. How would a vesper feel, if their magnum opus, the endowment that was supposed to go down in the arete records as its shining accomplishment, turned out to be a tool of transgression? And not through any of fault of its own (to the extent vespers have faults), but due to malign manipulations from its hosts?

Crepusules are allowed to exist as a mercy to the vespers who unwittingly brought it about.

(What judgment undergirds what gets crepuscularized and what doesn’t? Some theorize vespertine ‘arbiters’ that make such judgment, many counting them seven in number, matching a suggestive patterns (seven nymphs of the dream; seven laws in the septagrammaton). No conclusive evidence of arbiters has yet arisen. Some believed the archons, figureheads of a bat cult in the waning days of the myriad kingdoms, had the power to bring about crepuscules at will. Only myths of archons survive, their very existence is debated, and their feats are considered alongside those of other messianic figures.)

The other question to ask, though, is how.

In this sense, there are three types of crepuscular confinements

Unconfined Crepuscules

The chief example is the hemotectonic. The hemotectonic is an EZ because that’s where Tzic’zahd was, and she can no longer move, and all its phenomena are originate in her. In general, there are a number of zones that are simply focalized to some source that could move, but simply doesn’t. The crepuscule has no ability to actually enforce the confinement; it happens naturally.

Soft confinement

Consider the Dwimmermeal EZ. What actually makes it an EZ? If you try to create a dwimmermeal, it triggers the taboo and your vespers delete the instruction. If you take a grubsucker form the zone, it dies and decomposes. Overall, these effects can be modestly replicated: taboos require nothing but coordination among vespers. Grubsuckers are made by vespers, so of course the vespers can simply design them to self-destruct past certain compass cordinates. What’s important here is there’s nothing metaphysical about this zone; in a certain sense, it’s a “fake” exclusion.¹

Hard confinement

The omicron EZ is the foremost example of this. You cannot derive omicron-nrv anywhere; the reactions don’t seem to work. If you create omnicron-nrv in the zone, attempt to bring the mass pass the zone boundary results in force applied on the mass, dragging it backwards.

Hard confinement is rare, and seems to exclusively confine things that are, well, easy to confine. There are plenty of zones where enervate species are confined. There’s a zone where a certain radioative isotope is confined. There’s even a zone where a protein is confined. Attempted to synthesize it outside the zone will see it dissolve, albeit with some delay.

what unifies these effects is that every target of hard confinement is something with a particular oscillation mode that can be targeted.

The source of hard confinement is difficult to understand, partially because the most promsing theories hinge on planar physics, those enervate fields which permeate the whole planet. a notoriously difficult thing to get research clearance for, because the elemental planes are forbidden topics.

Indeed, hard confinement is believed by many to be a phenomena almost unrelated to the vespers‍ ‍‍—‍ at best, they are believed to be able to occasionally call upon it, but certain confinements seem to predate the development of agriculture itself, and several have seemingly no relation to aretology.

What is the force behind hard confinement? Certainly no arthropological power.