“The Shadow Kingdom” by Robert E. Howard is the first of Howard’s Kull stories, set in his fictional Thurian Age. It was first published in the pulp magazine Weird Tales in August 1929.
The story introduces Kull himself, the setting of Valusia, the supporting character Brule the Spear-slayer and the Serpent Men.
The story starts shortly after the Atlantean barbarian Kull has conquered Valusia and become its King. Kull is invited to a feast by the Pictish ambassador to Valusia, Ka-nu the Ancient. Despite the fact that the Picts are the ancient enemies of the Atlanteans, Ka-nu confides in Kull and tells him to expect the arrival of Brule the Spear-slayer later.
In the early night, Brule climbs into Kull’s bed chamber, identifying himself with a “bracelet of gold representing a winged dragon coiled thrice, with three horns of ruby on the head” that had been shown to Kull at the feast. Brule explains that Kull’s life is in danger and shows him secret passages that riddle the palace. Through these Kull sees that the guards outside his room are all dead and their bodies hidden, although they still seem to be on guard at the same time. A visit by Chief Councillor Tu, with exposition from Brule, reveals the truth as Tu attempts to assassinate the sleeping King but meets him awake and armed.
Brule reveals that the Serpent Men, an ancient pre-human race that had built Valusia but was almost extinct, ruled from the shadows, using their Snake Cult religion and ability to disguise themselves with magic. They intended to replace Kull with a disguised Serpent Man, just as they had done with his predecessors.
The next day, the Serpent Men again attempt to replace Kull. He and Brule are, through illusion, tricked into a separate room instead of the real council, surrounded by Serpent Men disguised as the councillors. Kull realises the trap in time, however, and the two barely defeat their attackers. Heading to the real Council Room, they see another Kull. The fake Kull is killed by the real one, revealing the fake as a Serpent Man and so also revealing the truth of the existence of Serpent Men in general. The story ends with Kull’s oath to hunt and destroy the Serpent Men for good.