"The Sorcerer's Jewel" by Robert Bloch
The HorrorBabble Podcast - A podcast by HorrorBabble - Tuesdays

"The Sorcerer's Jewel" is a Cthulhu Mythos story by Robert Bloch, first published in the February 1939 edition of Strange Stories, under the pseudonym, Tarleton Fiske. “Those forms were spawned in the nightmares and dreams of the Pit."