The Hyperborean cycle is a series of short stories by Clark Ashton Smith that take place in the fictional prehistoric setting of Hyperborea (present-ay Greenland). Various elements in Smith's cycle have been borrowed by H. P. Lovecraft, most notably the "toad-god" Tsathoggua. Because Smith in turn borrowed numerous Lovecraftian elements, the cycle itself may be regarded as a branch of the Cthulhu Mythos.