It was worshipped in Bal-Sagoth, a remnant colony of Atlantis. It has a "bird avatar" form, one of which was killed during the Dark Ages.
Groth-Golka is the lord of the "Fishers From Outside" (possibly the Shantaks).
Groth-Golka was created by Robert E. Howard for the non-Myths story "The Gods of Bal-Sagoth". Lin Carter incorporated these gods into the Mythos, but for a time confused Groth-Golka and Gol-goroth. Efforts have been made to untangle the confusion.