There's a significant omission with the version of this poem at The Eldritch Dark in the fourth stanza. The correct full reading of that stanza is as follows; the omission on The Eldritch Dark is the fourth line:
O land where dolent monsters mate!
I know the lusts that howl and run
When the red stones reverberate
The red, intolerable sun;
The soot-black lecheries that wail
From Hinnom to the moons of bale.
This poem was apparently written in 1935, but in terms of subject matter, it hearkens back to CAS' early poetry, especially some of the verses included in his first published collection (The Star-Treader and Other Poems (1912)).
The first section of the poem presents some incredibly vivid images of a tormented narrator adrift in a desolate wasteland:
I roam a limbo long abhorred,
Whose dread horizons flame and flow
Like iron from a furnace poured:
A bournless realm of sterile woe,
Where mad mirages fill the dawn
With roses lost and fountains gone.
That last line is wonderfully evocative; it's amazing what CAS could conjure in a mere six words!
The second section of the poem reinforces the idea that the narrator's exile in a horrific desert landscape is a metaphor for rejection by a paramour, and in the very last stanza we read a plea for reconciliation:
My heart, consumed yet unconsuming,
Burns like a dreadful, ardent sun,
The horror of strange nights illuming:
Shall yet I find the ways foregone,
And speak, before the heart of thee,
The still-remembered Sesame?
The aching expressed in those lines is profound, and CAS leaves the question unresolved: will the narrator find that elusive magic password to let him escape the wilderness and come home to his beloved?