Read "Thebaid" at The Eldritch Dark:
The version of this poem at The Eldritch Dark has a significant typo in line seven: the correct reading of that line is:
Thin out and vanish on the waste and vast
Joshi & Schultz's edition of CAS' The Complete Poetry and Translations mentions that this poem had a couple of alternate titles: "Arctica Deserta" and "Ultima Thule" (hence the image I've selected to accompany this post).
The theme of isolation is evident throughout this poem: isolation in such totality that it speaks even to separation from the divine:
What shall we do
For whom the heavens are throneless, and there is
No demon prince to supplicate and serve?
Although the solitude expressed in "Thebaid" has troubling aspects, there is also a note of freedom in these lines: "Where codes and cults, philosophies and gods / Thin out and vanish on the waste and vast". This landscape is remote, but it's also free of the detritus of human civilization, with its rigid social expectations and fabricated deities. Thus "Thebaid" strikes me as a wonderfully pure distillation of some of CAS' own values, given his dislike of progress and urbanity and his strong belief in the value of artistic expression and the creative life.