Read "The Medusa of the Skies" at The Eldritch Dark:
Clark Ashton Smith (CAS) substantially altered this sonnet between its original appearance in The Star-Treader and Other Poems (1912) and a later appearance in Selected Poems (1971). I'll focus on the latter text, which is also available on The Eldritch Dark.
As an aside, it's worth noting that CAS later translated this poem into French, with the title "La Méduse des cieux".
This poem presents quite a grim image of moonlight:
Under her beams the breasted lands assume
Dead hues, and charnel shapes unceremented;
And shadows that towering sepulchers might shed
Move livid as the shadows on dials of doom.
In the closing sestet, the grim character of these lines resolves into a personification as "reptant Death at last rears absolute", and the poem closes with an echo of the title, strongly associating the moon with the baleful powers of the mythical Gorgons.
Although I've read less than two hundred poems by CAS so far, this is the third to include "Medusa" in the title, and The Eldritch Dark lists two others that I have not yet gotten to. While I can't yet draw any big conclusions, it's interesting that CAS made quite a bit of use of this theme from classical mythology, tapping into the raw terror associated with the character of Medusa.