"Parabola-linen crumbles in sunlight. The mushroom wines of the Neath are not kindly received in the wine-shops of Italy and France. Prisoner's honey loses all its virtue."[1]
The Sun is the Judgement of the Earth and of Mankind - though it can only govern those of us dwelling on the Surface.
Incandescent, and Far More Than Just Gas[]
To Surface-dwellers, the Sun is a benevolent force, even one worthy of worship. Some who have descended to the Neath, however, have begun to question its virtue. This is primarily because the Sun is brutally effective at enforcing its laws; denizens of the Neath who have lived too long often drop dead or even disintegrate upon reaching the Surface, and most of the Neath's fantastic delights are reduced to their normal variety under sunlight. Parabolan entities are cooked almost immediately, as they too Are-Not. And stories about the Neath are simply not believed because of all this.[1]
The Sun does have a view of the Neath, in Aestival, where there is a gap in the roof. Despite its deadly effects, sunlight is highly addictive to denizens of the Neath (who doesn't love a warm summer day?) and many of them go out with a smile.[2] Neath-dwelling humans who are severely starved of sunlight may enter a trance of sorts when exposed to sunlight in small quantities, such as through a sunlight-filled mirrorcatch box, causing them to chant an infamous mantra: "THE SUN! THE SUN!"[3]
Albion's murdered star is not the Sun; Sol is just fine in the Sunless Skies timeline.
Once Upon A Time[]
The Sun's story is that of fleeting desires and the horrors of love. Long before the time of the First City, the Sun fathered the Mountain of Light with the Bazaar. Such a union between a Judgement and its messenger was scandalous even for the stars, so the Sun stored Stone in the Neath to avoid execution. Then the Sun fell in love with a different star, and in a rather callous move, had the Bazaar deliver a love letter to her. The Bazaar discovered that the reply contained a rejection of the Sun's love, so the Bazaar is now biding its time before delivering the message in order to prevent the Sun from drowning in its own tears.[4]