This is another poem unpublished in Clark Ashton Smith's (CAS) lifetime, and not available on The Eldritch Dark, so let's start with the text itself:
I mark yon ruddy star go down
O'er hills mysterious with night,
And far-off peaks that darkly frown
In towering and impassive might.
At last it trembles on the crest
Of some vague, mist-enshrouded height,
A moment seeming to arrest
Its downward and unswerving flight.
This is a fairly straightforward poem, and yet there are some strong images in these brief lines: "far-off peaks that darkly frown", "it trembles on the crest", "downward and unswerving flight". Proof that even in a minor item from the corpus, CAS can invoke a response from a reader who makes the effort to engage with the author's rich language.