Arthur Machen (1863-1947) was a Welsh author and actor best known for his fantasy/horror tales set in the decadent Edwardian era. He was a major influence on HP Lovecraft, who considered him a modern master who could create "cosmic horror raised to its most artistic pitch." In addition to The Great God Pan, Lovecraft also praised "The Novel of the Black Seal" and "The Novel of the White Powder" (The Three Imposters) as "approach[ing] the absolute culmination of loathsome fright" and used them as the basis for his own works Cool Air and The Colour Out of Space. Along with his American contemporary Robert W. Chambers, Machen is noted today as one of the forerunners of the Cosmic Horror genre Lovecraft pioneered.

Machen was born to a poor vicar in rural Wales. As an adult, his poverty was greatly ameliorated by an inheritance left him by several Scottish relatives, which also enabled him to devote more time to writing. He took up acting shortly after the death of his first wife in 1899 and associated with Aleister Crowley and his circle, mostly out of curiosity. Machen is also responsible for "The Angels of Mons", a fictional tale he wrote for a newspaper during World War I that many subsequently treated as a true story - despite his insistence that it was no such thing.

After a brief period of popularity in the 1920s, Machen's fortunes faded. On his eightieth birthday in 1943, however, a literary appeal was launched to formally recognize him as a distinguished man of letters. Signers of the appeal included T.S. Eliot, Bernard Shaw, Walter de la Mare, Algernon Blackwood, and John Masefield. Its success allowed Machen to live out his final years in relative comfort.

• The Great God Pan
• "The Inmost Light"
• "The Shining Pyramid"
• The Three Impostors
• "The Red Hand"
• "The White People"
• The Hill of Dreams
• "Ornaments in Jade"
• "The House of the Hidden Light"
• The Terror
• The Green Round
• The Children of the Pool

• Agent Mulder: Many are featured in his writings, though Dyson is almost certainly the most notable.
• Agent Scully: Phillips, to Dyson's Mulder.
• All First-Person Narrators Write Like Novelists: The Three Imposters is made of this.
• Amateur Sleuth / Occult Detective: Dyson in "The Shining Pyramid" and The Three Imposters.
• Apocalyptic Log: "The White People"
• Author Avatar: Several of Machen's protagonists were born to poor vicars, struggle to write in poverty, and/or live off an inheritance left to them by deceased relatives. The imaginative and inquisitive Dyson is a prominent example, as is Lucian Taylor in The Hill of Dreams.
• Black Speech: The language of the Little People is described this way.

• Body Horror: The climax of "The Novel of the White Powder." Also
• Break the Cutie: Poor Mrs. Black ("The Inmost Light").
• Campbell Country: Was way before Campbell, though.
• Character Filibuster: The Three Imposters is made up of this. Miss Lally even recites from memory a letter that is several pages long. Characters in other stories are also prone to Walls of Text.
• Child by Rape: in The Three Impostors.
• Cosmic Horror: One of the genre's forerunners.
• Creator Breakdown: Inverted. After his wife died, Machen went through a great deal of personal turmoil and soul searching. He then converted to Christianity at the turn of the century^[1] and used his newfound sense of inner peace to write two particularly upbeat novels, The Great Return and The Secret Glory
• Creator Cameo: Machen would appear as the nameless protagonist in some of his later stories, such as The Happy Children or Out of the Earth. He was also the Greek Chorus and Decoy Protagonist of The Terror.
• Creepy Child: The girl in "The White People."
• Don't Go in The Woods: Several people go missing after venturing off in isolated rural areas.
• Driven to Suicide: The subject of .
• Fair Folk: Machen went straight back to the earliest legends and created a particularly nightmarish version he called the "Little People."
• Go Mad from the Revelation
• Half-Human Hybrid:
  • In The Three Imposters, .
  • The eponymous character in
• Human Sacrifice: The Little People do this.
• In Name Only: The radio adaptation of The Red Hand done for The Weird Circle, a show with a history of doing this for their book-to-radio adaptations. Oddly enough, while it had absolutely nothing in common with the original story, it did have a minor (and probably unintentional) similarity to one of Machen's other works: The Three Impostors.
• Mad Scientist: Dr. Black. (Professor Gregg was more misguided.)
• Mystery Magnet: Dyson just comes across the weirdest things completely by chance.
• Never Recycle a Building: At the end of "The Three Imposters" there's an abandoned mansion within walking distance of London and completely accessible to passers-by, yet is still untouched except for the natural processes of decay.
• Nightmare Face: Quite a few instances of visages almost too horrible to describe.
• Nightmare Fuel Station Attendant: The girl whose journal makes up most of "The White People" doesn't really seem to get how bizarre the things she's talking about are, or the deeper implications of the stuff she's seen.
• Nothing Is Scarier: "The White People."
• Platonic Cave: Machen's favorite theme.
• Scenery Porn: The man had a gift for making you feel like you were really in the settings of the stories.
• Shaggy Search Technique: A common element of Machen's early fiction, especially in The Three Imposters.
• Supernatural Fiction
• Take Our Word for It: As with Lovecraft later on, a lot of horrifying stuff is only hinted at.
• Things Man Was Not Meant to Know
• Unreliable Narrator: The title characters in The Three Impostors, though the title is pretty much a dead giveaway that this trope applies.
• Was Once a Man: .
• Wild Wilderness