The phrase “the Devil’s fane” comes from a passage in The Satanic Bible by Anton Szandor LaVey, who founded the original modern atheistic Satanic organization, the Church of Satan, in 1966.
“When all religious faith in lies has waned, it is because man has become closer to himself and farther from ‘God’; closer to the ‘Devil.’ If this is what the devil represents, and a man lives his life in the devil’s fane, with the sinews of Satan moving in his flesh, then he either escapes from the cacklings and carpings of the righteous, or stands proudly in his secret places of the earth…until that day when he may come forth in splendor proclaiming ‘I AM A SATANIST!’”
from “The God You Save May Be Yourself”
While LaVey’s Satanic Bible provides the proximal source of the phrase and the concept it denotes, the history of those words and their use in the philosophical and religious battle for human hearts and minds runs far deeper. If you have a bit of time to explore this deeper history of “the Devil’s fane” and its significance to modern Satanism, click here for more info.