Cthulhu Mythos
Lin Carter and Clark Ashton Smith adapted the race for inclusion in the Cthulhu Mythos, inspired by H. P. Lovecraft's short story "The Nameless City", which refers to an Arabian city built by a pre-human reptilian race. Lovecraft's story "The Haunter of the Dark" explicitly mentions the "serpent men of Valusia" as being one-time possessors of the Shining Trapezohedron. However, the Cthulhu Mythos were already connected to the works of Robert E. Howard (a contemporary and correspondent of H. P. Lovecraft as well as a direct contributor to the Mythos itself). In this case, the Serpent Men were created for the very first Kull story, the character of Kull later made an appearance in a Bran Mak Morn story, Kings of the Night, while in another such story, Worms of the Earth, Bran Mak Morn explicitly refers to Cthulhu and R'lyeh. Many Conan stories by Howard are also part of the Mythos.
Read more about this topic: Serpent Men