Does this contain a cosmic riddle?

Question

I have recently returned from travelling the globe, and while I saw many sights on my Ulyssian adventure, one in particular remains with me...

While walking through an ancient Middle Eastern cave system, I stumbled upon a huge cavern blazing with torches. On the far wall, illumined by the firelight, I beheld a massive inscription that appeared to be a riddle.

I have no idea whether this inscription is old or new, but I took a photo which you can see below.

The text was as follows:

This thing is a poem, a riddle containing:
   Cosmic Grandeur’s Clarion;
A statement about one who, camels sustaining,
   Makes disciples carrion;
For none, yet for all, ‘tis a tale involving
   Men who will defeat us;
It sings for celestial dawn, for evolving
   Ape and nascent foetus.

What thing is the riddle cluing? Give me a three word phrase (in whichever language you please).

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_{Note all of the introductory text and the image is solely there for flavour. The 8-line italicized riddle stands alone, and all you need use to solve it is the plaintext.}

Answer 1

I think the solution is

Also Sprach Zarathustra or, if you want it in English, Thus Spake Zarathustra. (Both of these are three words, of course.) This is the title of a book by Nietzsche, which in turn gave its name to a piece of music by Richard Strauss which is used prominently in the soundtrack of Stanley Kubrick's 2001: A Space Odyssey. (Note the "Ulyssian adventure" in the flavourtext at the start.) The specific thing we're after is the piece of music.

This thing is a poem, a riddle containing:
   Cosmic Grandeur’s Clarion;

Strictly, it's a tone poem. The opening motif goes C-G-C, hence the second line here. It's sometimes referred to as the "world riddle" motif, apparently, hence the "riddle" in the first line.

A statement about one who, camels sustaining,
   Makes disciples carrion;

The statement "Thus spake Zarathustra" is clearly about the prophet Zarathustra. The name of Zarathustra/Zoroaster is thought to mean something like "one who can handle camels". He "makes disciples carrion" in the sense that Zoroastrians don't bury their dead but expose them to the elements (and to scavengers) in special towers built for the purpose.

For none, yet for all, ‘tis a tale involving
   Men who will defeat us;

That is to say, Nietzsche's Übermenschen. The book Thus Spake Zarathustra is subtitled "A book for all and none".

It sings for celestial dawn, for evolving
   Ape and nascent foetus.

And here we are looking at the Kubrick movie, which starts with apes and ends with David Bowman transformed into the "Star Child". The movement of Also Sprach Zarathustra that's used in 2001 is entitled "Introduction, or Sunrise" -- and in fact it's used in three places in the movie: the opening titles involving sun, earth and moon; the first scene with the apes; and the final scene with the "Star Child".

Credit where due:

Some bits of the above I didn't know until OP kindly pointed them out, or hinted at them, in comments: the nickname of the C-G-C motif in Also Sprach Zarathustra, the funerary customs of Zoroastrians, the subtitle of Nietzsche's book, and the specific points in 2001 where Strauss's music is used.