Amalric, the son of a noble family from Aquilonia’s great house of Valerus, finds himself far south of Stygia, traveling through the desert in the company of three Ghanata bandits: Gobir, Saidu, and Tilutan. Tilutan, a ferocious black giant, brings an unconscious girl he has found in the desert, sparking tension among the group. Amalric, feigning indifference, uses cunning to kill Gobir and Saidu in a fight and then defeats Tilutan in a brutal struggle. The girl, Lissa, revives Amalric, and they converse in a shared tongue. Lissa explains she fled her home city, Gazal, a nearby oasis city populated by a dreamy, scholarly, and peaceful people.

Upon reaching Gazal, Amalric discovers a city in ruin except for a solitary southeastern tower. The citizens reveal that a supernatural being inhabits the tower, worshipped by desert nomads, and occasionally preys upon the people. Amalric bonds with Lissa, who expresses her longing to escape her stagnant life. One night, they hear terrifying cries from the tower, and Amalric investigates. He encounters a supernatural creature in human form and defeats it using a Kushite incantation, but not before the being curses him with vengeance. Amalric finds Lissa safe but learns they are being pursued by ghastly black riders summoned by the creature's death.

As Amalric and Lissa flee westward, they are saved at the last moment by a group of riders led by Conan the Cimmerian, Amalric’s former companion who had been presumed dead. Conan explains how he was taken to the semi-mythical city of Tombalku after being captured in the desert. Tombalku is ruled by two kings: Sakumbe, a corpulent and decadent black man, and Zehbeh, a lean brown-skinned man. Conan’s past connection with Sakumbe earns him favor, and he rises to prominence as the general of Tombalku’s cavalry. However, tensions simmer within the city due to competing factions among its rulers, priests, and various ethnic groups.

Conan takes Amalric and Lissa to Tombalku, where they witness the execution of Daura, Zehbeh’s priest, by Askia, Sakumbe’s fanatical high priest. Sakumbe, though corrupt and indulgent, remains the true power in Tombalku due to his influence over the black tribes. Conan schemes to eliminate Zehbeh and align himself with Sakumbe, but this alliance crumbles when Askia turns on Sakumbe, destroying him with dark magic. Chaos erupts as Zehbeh’s forces attack Tombalku, leading to a devastating civil war. Amidst the destruction, Amalric, Conan, and Lissa fight their way out of the city and escape into the desert.