Any statement about the fifteenth Aethyr belongs to one of three layers of the record, and they are roughly three centuries apart. Saying which layer a claim comes from is most of what can honestly be said about an individual Aethyr.
The diaries, 1580s
The name OXO, its place as the fifteenth of the thirty, and the governors assigned to it all come from the scrying sessions of John Dee and Edward Kelley in the 1580s. In that material the thirty Aethyrs divide the earth between ninety-one governors: twenty-nine Aethyrs hold three each and the thirtieth holds four. This atlas carries all ninety-one, and the arithmetic can be checked against them.
The Golden Dawn, late nineteenth century
The Hermetic Order of the Golden Dawn took Dee's material into its own curriculum and reorganised it, but its Enochian teaching concentrated on the four Watchtower tablets and the Tablet of Union. The thirty Aethyrs were comparatively little developed there. A claim about an Aethyr is therefore rarely a Golden Dawn claim, which is worth knowing because the order is often named as the source for Enochian material generally.
Crowley, 1900 and 1909
Almost everything said about the character of an individual Aethyr in modern circulation comes from Aleister Crowley. By his own account he began the series in Mexico in 1900 and completed it with Victor Neuburg in the Algerian desert in late 1909, and the record was published as The Vision and the Voice. Those descriptions are Crowley's visionary record of 1909, not Dee's, and they are not in the sixteenth-century diaries at all.