"The Dark Demon"

 

by Robert Bloch

originally published Weird Tales, November 1936

Edgar Gordon, horror author extraordinaire, has died ... maybe.  

Our Narrator, a fellow horror-author, had corresponded with him and, finding he lived in the same town, become a personal friend of Gordon's.  

Gordon is a strange one who bases his stories on his vivid dreams, which often take him into alien worlds and involve strange alien beings.

Gordon's writings get stranger and stranger and so does he.  He begins to claim he's the the chosen messiah of The Dark One, aka Nyarlathotep, who is to carry Ny's message to the world.  

O.N. mostly avoids Gordon after that, but one night is drawn to Gordon's place where he finds Gordon has taken on a non-human form.  He shoots him.

This one has a lot of atmosphere and effectively conjures up some of the bizarre, space-horror of HPL and Clark Ashton Smith.  But its a bit thin dramatically and has a weak ending.