The entire time I was re-reading Clark Ashton Smith's The Charnel God, I kept thinking, "I bet Robert E. Howard liked this one."
A little research proves that true. On page 197 of Volume 3 of The Collected Letters of Robert E. Howard, REH writes to CAS of the Charnel God:
"That story is really a tremendously powerful thing, sinister figures moving mysteriously against a black background of subtle horror. I don't know when I've read anything I admired more."