The Sky has cracked into potter's shards,
Fire sweeps the compass of Heaven,
Ash has shrouded all sun, choked all seed,
The Halaroi howl piteously at the Gates,
Dread Famine stalks my Mansion.
Brother Siöl, Viri begs your pardon.
This has two sentences. So we can take it as two parts.
In the first sentence, and the epistle as a whole, the first character after a carriage return is capitalized, we can probably ignore these capitalizations as insignificant, mere style.
In the second part, two proper nouns are capitalized.
In the first part, common nouns are not capitalized, but Famine is capitalized (used in context as though it were a proper noun and Famine represented an anthropomorphicpersonification), and a race name is capitalized, Halaroi, also used as a proper noun.
This leaves three words standing out in the middle of a sentence and possessing unusual capitalization, signifying perhaps additional meaning that justifies their capitalization.
Heaven, Gates, Mansion
Heaven
Gates
Mansion
We know the Heavens are the skies above the surface of the earth.
We know that Mansions are the bowels and pits beneath the surface of the earth.
We could posit that this suggests a Heaven/Hell traditional dichotomy, with the mansions as Hell.
We could further posit that The Gates suggests a middle ground, or a middle earth, in between the Heavens above and the Mansions (Hell) below. Or, more literally, The Gates suggest there is literally a Gate between Heaven and Hell, that connects the two together and affixes them to each other.
Interestingly, You could argue a Great Medial Screw might be a lynchpin device that attaches Heaven to Hell (mansion) as literally as a screw attaches drywall to a stud. Interestingly, when characters approached such a Great Medial Screw, they were attacked by a creature described as bringing Hell with him, a creature who complained/screamed that the Gates were unguarded when they approached the screw... Almost as if they were approaching the Gates.
Interestingly, we have a building/trap constructed on top of a similar Screw at Viri, and the assessment of this depth/pit was described as "a warning to those who would delve to deep." Which could perhaps be interpreted as, if you dig deeper into hell in your Screw/Gate, you open an even bigger Gate, a Gate that would be harder to guard.
Interestingly, we also have a story about the holiest of holy humans to ever live ascending to Heaven at a Screw/Gate.
Interestingly, the Halaroi pits, where they were imprisoned was very near the Great Medial Screw, which could suggest they were perhaps part of the guard, or more like the great seal of the library of sauglish or shaeonanra's circle of immortality, perhaps The Halaroi were lashed to the Screw to power it, and as they starved, they howled piteously at the Gates.
All of this comes together to suggest that the nonmen were committing unfathomable atrocities and perhaps literally tried to pin heaven to earth with their screws, perhaps to allow them to ascend, perhaps to allow them to descend. But perhaps these screws had consequences beyond, galactically far beyond anything the nonmen ever conceived, and the portals they believed connected the heavens to the earth was causing all sorts of havoc throughout the universe and caused a ship to fall from the heavens to the earth, and very nearly into the deepest mansions.
Which would all go to explain the second part of the quote as "begs your pardon" As literally what it is asking for, not a metaphor for an apology or a metaphor for a plea for assistance. It's a plea for forgiveness and absolution because Viri was the cause of the suffering detailed in the first part of the quote.
