The Secret Chiefs have played an important part in the development of Thelema. Their ideological origin seems to be with the Hidden Mahatmas of the Theosophists in the XIXth Century ev. But they may also belong to the apocryphal origins of beings like the Nephilim and Annunaki. And today, they may even be extraterrestrials; our modern angels.
In the sermon for our October 2014, Rosicrucian Mass, we discussed the symbols of Babalon and the Beast, as they are shown to us in Liber Cheth. These symbols are originally presented in the Starry Gnosis; the amazingly eternal human archetype; drawn into the sky map by the ancients or Secret Chiefs.