From Greek ἔμπυρος empyrus "in or on the fire (pyr)."
In western religions, the highest of the heavens, explored by Dante in his Divine Comedy.
In Kabbalah, this region corresponds to Neptune and the sephirah Kether.
"In these studies of Kabbalah, we need to be practical; there are authors who write marvels, but when one looks at them, one realizes that they have not lived what they have written; they did not experience it in themselves, and that is why they are mistaken. I understand that one must write what one has directly experienced by oneself. I have proceeded in this way for my part."