Bran Mak Morn, King of the Picts, vows vengeance on Titus Sulla, a Roman governor, after witnessing the crucifixion of a fellow Pict. He seeks forbidden aid from the Worms of the Earth, a race of creatures who Bran Mak Morn's ancestors banished from their kingdom centuries ago. They were once men, but millennia of living underground caused them to become monstrous and semi-reptilian. Searching for a contact with these creatures, Bran Mak Morn encounters a witch who lives in a secluded hut, shunned by her neighbors, who was born from a sexual encounter between one of the "Worms" and a human woman. The witch's price for helping him is "one night of love" which her human-half craves - as men in general are repelled by her reptilian traits. Bran Mak Morn, though also himself repelled, agrees to pay the price. In exchange, she tells him of a barrow where "The Black Stone", a religious artifact of great importance to the "Worms", is hidden. Stealing the Black Stone is a highly risky enterprise - if caught by the "Worms", Bran Mak Morn would die in torment "as no man had died for a thousand years". Fortunately, the barrow is unguarded and he manages to carry out his theft by hiding the Stone at the bottom of a lake. To get it back, the "Worms" agree on delivering Sulla to him. This they proceed with, undermining and destroying a Roman fortress known as "Trajan's Tower" before snatching the Roman governor into their tunnels. Mak Morn intended, once Sulla was delivered, on challenging him to a duel to the death. However, Sulla's mind is damaged from his encounter with the horrific Worms of the Earth. Instead, Bran Mak Morn slays him in mercy rather than vengeance, realizing how some weapons are too foul to use, even against Rome.
Reception
In a 1932 letter to August Derleth, Clark Ashton Smith, discussing the current issue of Weird Tales, stated that "Howard’s “Worms of the Earth” seems to be the one real first-rater." In an obituary for Howard, H. P. Lovecraft said " Few readers will ever forget the hideous and compelling power of that macabre masterpiece, "Worms of the Earth"". Robert Weinberg called "Worms of the Earth" "an effective blend of horror and adventure", and said it was one of Howard's "best works".
