Word for a "blackened" and "abhorred" sky

Salutations, I am looking for a single word that alludes to a sky that is very hated and repulsed due to its utter deathliness.

for example: "God's angels swarmed into the "nihility-like sky (THE REQUESTED WORD)" and painted it with a heavenly hue of red"

Now, it is most imperative for this word not to have any connotation with "incarnadine" and that "hell-firey" atmosphere which dystopian skies so often are presented with, but rather a sky abhorred for just how "dead" and "oblivion-like" it is--so I guess it would be a more by melancholy, maddening just because of how lifeless it is.

Thank you with perpetual heaven-lit skies.

"Firmament" is a good one, and has a mythological feel which would appear to fit.

"Welkin" might also be a possibility, but it's more likely to be unfamiliar to the reader.

From "Dictionary.com" :

Firmament [ fur-muh-muh nt ] noun. the vault of heaven; sky.

Welkin [ wel-kin ] noun Chiefly Literary. the sky; the vault of heaven.