There are many theories in-universe and out on why exactly going back to the surface instantly fries you if you’ve died in the Neath or even simply been down there for a long time. Here’s a theory I’ve been throwing around in my mind for a while that has resurfaced in my mind since some of the recent exceptional stories involved death and Parabola.
As we know, Parabola is a realm entered through mirrors and dreams and is considered Is Not, essentially considered not to exist by the Laws of the Judgments/Stars. Anything from Parabola that is exposed to the light of the Sun or other stars in instantly destroyed for violating the Law that they don’t exist. It’s a very philosophical topic but what the Jugdments deem does not exist simply does not exist. Of course, down in the Neath where the blinding irrigo lights of the Nadir keep the Laws from fully functioning, Is Not from Parabola can escape into our reality. My theory is a simple one. The citizens of London and all the Neath are practically right next door to Parabola and are constantly exposed to it through mirrors and especially dreams, and that’s when we’re not going there directly such as when we go to the Mirror Marches. What if the exposure to Parabola is working like radiation of sorts and becoming a part of our very being by being exposed to it for so long? Beings from Parabola want nothing more than to become reality as we know the Fingerkings love to possess people just to walk around and be real for once. All this exposure is making us appear as Is Not in the eyes of the Judgments and they strike us down when we go to surface because we don’t exist according to their Laws.
This would explain why even those that don’t die can be slain upon visiting the surface if they’ve been down here for a while. Being down in the Neath for so long next to Parabola has made us Is Not.
Sunlight’s effects on things from the Neath can be far from instant. The husband of the Empress’s Shadow spent quite some time in the Neath and survived for 99 days after returning to the Surface.
Things which come entirely from the Neath, such as Prisoner’s Honey, perish upon arrival in the surface. Humans, even those born in the Neath, come at least partially from what is, and can survive short periods on the surface. Darkdrop coffee is an exception to the normal destruction of Neathy products brought above, so its origins may well be in surface coffee brought below.
Entities of sufficient power are unaffected by time below. The Masters are unconcerned, and in the Chilly Future destiny path they are unharmed by returning with the Bazaar to the High Wilderness. The Dawn Machine can outright say “NO” to ordinary sunlight, and even shield lesser things from the usual deterioration, as shown by Dawn’s Law in Sunless Sea. I’d attribute that to the fact that it produces its own laws of reality which displace those of the older judgements.
I wouldn’t say that everything in the Neath becomes is-not, but I do think that people and things which come below are infected by what is not, and the purging of that infection by sunlight can prove fatal at advanced stages of infection.
I think calling Is Not a metaphor for both radiation poisoning or infection work equally well. The crux of my theory is that long term exposure to Is Not causes it to become part of someone enough that the Judgments see them as Is Not and strike them down. Certain higher tier beings such as the Masters would probably have a sort of resistance or immunity to Is Not corruption. edited by loredeluxe on 8/1/2017
I think the whole thing about becoming ‘Is not’ can be more easily explained by the Irrigo which permeates the entirety of the neath, rather than being close to Parabola, especially considering you can even become an ‘Is not’ to the Neath after enough exposure to Irrigo, during seeking.