"The Devil-God" by Frank Belknap Long

Published in 1925.

four-in-hand: the only clothing related reference I can find for this is a necktie tied in a specific way. A necktie sans shirt? LOL! I mean, do you do occasionally see it, mostly in advertisements, especially on extremely ripped men, but this is an old witch doctor. But, when you are the witch doctor, who is going to mock you? You get to do whatever you want!

trucidate: to slaughter, massacre, kill

Aubrey Beardsley: an English illustrator of the late 19th century

Rops: Félicien Rops, a Belgian artist of the 19th century

John Martin: there's a rather generic name, but perhaps the English painter for the first half of the 19th century?

Goya: Francisco Goya, a Spanish romantic painter and printmaker of the 18th and early 19th centuries.

Sir John Mandeville: author of "The Travels of Sir John Mandeville", a travel memoir of a 14th century Englishman traveling across the Islamic world, and to India and China. It is doubtful if John Mandeville is a real person, and the book appears to be a conglomeration of accounts written by a number of other people. But it was a popular book, and quite fantastical the further east he went.

The picture used is the illustration for the story from Weird Tales (June, 1925) by Andrew Borsnatch