This poem was unpublished in the lifetime of Clark Ashton Smith (CAS), and not available on The Eldritch Dark, so let's start with the poem itself:
A voice decreed: "Let there be no more light:
Reveal the gulfs and systems utterly."
The veils and limits that infinity
Hath for its shields, were smitten of the light;
Horizonless, unsealed of depth or height,
One after one, unto my scrutiny
The deeps and their invested suns leapt free,
And billow-like, rolled on the shores of sight.
Nor interstice nor film of gloom remained
To dull the stars' intolerable host
Or stay the firmament's immeasured press,
That smote with revelation unrestrained,
Till 'neath the weight of vastness uttermost
My spirit's walls fell into nothingness.
This poem shares a very similar theme to "A Dream of Oblivion", which I discussed a couple of blog posts back. This present poem "The Revelation" seems much the more polished of the two works, taking the form of a sonnet with a fairly regular abcabc rhyme scheme.
The opening of this poem is quite effective, featuring a dramatic quote from an unsourced voice, an opening that is effectively matched by the thrilling final lines: "Till 'neath the weight of vastness uttermost / My spirit's walls fell into nothingness."
The phrase "vastness uttermost" could be recognized as the stamp of CAS even outside the context of this poem. While these lines were likely written under the influence of George Sterling, it is impressive to see the very young CAS (likely still a teenager when this was written) taking ownership of a personal cosmic vision that he would develop so completely in the coming years.