Complex sentence: Their first appearance was in a King Kull short story, "The Shadow Kingdom," first published in "Weird Tales" (August 1929) and later republished in the collection "King Kull" (1967) by Lancer Books.
Split into simpler sentences: Their first appearance was a King Kull short story, "The Shadow Kingdom". This story was published in "Weird Tales" (August 1929) and republished in the collection "King Kull" (1967) by Lancer Books.